internal server error

Hi i hosted my own forge server on 1.15.2 with mods. when trying to connect i get the massage internal server error. 

please help.

this is what the cmd of the server.

C:\Users\jakob\Desktop\forgeserver 1.15.2>"C:\Program Files\Java\jdk-11.0.12\bin\java.exe" -Xmx4096M -Xms4096M -jar forgeserver1.15.jar nogui
2021-09-29 18:59:48,368 main WARN Advanced terminal features are not available in this environment
←[32m[18:59:48] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher running: args [--gameDir, ., --launchTarget, fmlserver, --fml.forgeVersion, 31.2.55, --fml.mcpVersion, 20200515.085601, --fml.mcVersion, 1.15.2, --fml.forgeGroup, net.minecraftforge, nogui]
←[m←[32m[18:59:48] [main/INFO] [cp.mo.mo.Launcher/MODLAUNCHER]: ModLauncher 5.1.2+70+master.2845bb9 starting: java version 11.0.12 by Oracle Corporation
←[m←[32m[18:59:49] [main/INFO] [ne.mi.fm.lo.FixSSL/CORE]: Added Lets Encrypt root certificates as additional trust
←[m←[32m[18:59:50] [main/INFO] [mixin/]: SpongePowered MIXIN Subsystem Version=0.8.2 Source=file:/C:/Users/jakob/Desktop/forgeserver%201.15.2/libraries/org/spongepowered/mixin/0.8.2/mixin-0.8.2.jar Service=ModLauncher Env=SERVER
←[m←[32m[18:59:50] [main/INFO] [STDERR/]: [jdk.nashorn.api.scripting.NashornScriptEngine:<init>:143]: Warning: Nashorn engine is planned to be removed from a future JDK release
←[m←[32m[18:59:51] [main/INFO] [cp.mo.mo.LaunchServiceHandler/MODLAUNCHER]: Launching target 'fmlserver' with arguments [--gameDir, ., nogui]
←[m←[33m[19:00:03] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, destination] and [teleport, targets] with inputs: [Player, 0123, @e, dd12be42-52a9-4a91-a8a1-11c01849e498]
←[m←[33m[19:00:03] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, location] and [teleport, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
←[m←[33m[19:00:03] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, location] and [teleport, targets] with inputs: [0.1 -0.5 .9, 0 0 0]
←[m←[33m[19:00:03] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, targets] and [teleport, destination] with inputs: [Player, 0123, dd12be42-52a9-4a91-a8a1-11c01849e498]
←[m←[33m[19:00:03] [main/WARN] [minecraft/Commands]: Ambiguity between arguments [teleport, targets, location] and [teleport, targets, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
←[m←[32m[19:00:03] [Server thread/INFO] [minecraft/DedicatedServer]: Starting minecraft server version 1.15.2
←[m←[32m[19:00:05] [modloading-worker-3/INFO] [ne.mi.co.ForgeMod/FORGEMOD]: Forge mod loading, version 31.2.55, for MC 1.15.2 with MCP 20200515.085601
←[m←[33m[19:00:05] [modloading-worker-2/WARN] [minecraft/EntityType]: No data fixer registered for entity boar
←[m←[33m[19:00:05] [modloading-worker-2/WARN] [minecraft/EntityType]: No data fixer registered for entity animecow
←[m←[33m[19:00:05] [modloading-worker-2/WARN] [minecraft/EntityType]: No data fixer registered for entity angry_chicken
←[m←[32m[19:00:05] [modloading-worker-3/INFO] [ne.mi.co.MinecraftForge/FORGE]: MinecraftForge v31.2.55 Initialized
←[m←[32m[19:00:06] [Server thread/INFO] [minecraft/DedicatedServer]: Loading properties
←[m←[32m[19:00:07] [Forge Version Check/INFO] [ne.mi.fm.VersionChecker/]: [forge] Starting version check at https://files.minecraftforge.net/maven/net/minecraftforge/forge/promotions_slim.json
←[m←[32m[19:00:07] [Server thread/INFO] [minecraft/DedicatedServer]: Default game type: ADVENTURE
←[m←[32m[19:00:07] [Server thread/INFO] [minecraft/DedicatedServer]: Generating keypair
←[m←[32m[19:00:07] [Server thread/INFO] [minecraft/DedicatedServer]: Starting Minecraft server on *:61000
←[m←[32m[19:00:07] [Server thread/INFO] [minecraft/NetworkSystem]: Using default channel type
←[m←[32m[19:00:08] [Forge Version Check/INFO] [ne.mi.fm.VersionChecker/]: [forge] Found status: AHEAD Current: 31.2.55 Target: null
←[mWARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by net.minecraftforge.fml.common.ObfuscationReflectionHelper to method java.util.BitSet.trimToSize()
WARNING: Please consider reporting this to the maintainers of net.minecraftforge.fml.common.ObfuscationReflectionHelper
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
←[32m[19:00:08] [Server thread/INFO] [minecraft/DedicatedServer]: Preparing level "world"
←[m←[32m[19:00:08] [Server thread/INFO] [minecraft/SimpleReloadableResourceManager]: Reloading ResourceManager: scoobydoo1.15__02.jar, leveluphp-mc1.15.2-forge-5.1.2.jar, forge-1.15.2-31.2.55-universal.jar, Default, datapacks.zip
←[m←[1;31m[19:00:08] [Server thread/ERROR] [minecraft/MinecraftServer]: Failed to reload data packs
java.util.concurrent.ExecutionException: com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected name at line 8 column 2 path $.
        at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:395) ~[?:?] {}
        at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1999) ~[?:?] {}
        at net.minecraft.server.MinecraftServer.func_195568_a(MinecraftServer.java:1467) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at net.minecraft.server.MinecraftServer.func_195560_a(MinecraftServer.java:450) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at net.minecraft.server.MinecraftServer.func_71247_a(MinecraftServer.java:363) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:212) [?:?] {re:classloading,pl:accesstransformer:B}
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:613) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at java.lang.Thread.run(Thread.java:834) [?:?] {}
Caused by: com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected name at line 8 column 2 path $.
        at com.google.gson.Gson.fromJson(Gson.java:902) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.Gson.fromJson(Gson.java:852) ~[server-1.15.2-extra.jar:?] {}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.prepareOverrides(LevellingConfigManager.kt:26) ~[?:5.1.2] {re:classloading}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.prepare(LevellingConfigManager.kt:38) ~[?:5.1.2] {re:classloading}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.func_212854_a_(LevellingConfigManager.kt:14) ~[?:5.1.2] {re:classloading}
        at net.minecraft.client.resources.ReloadListener.func_215270_b(SourceFile:11) ~[?:?] {re:classloading}
        at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1700) ~[?:?] {}
        at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1692) ~[?:?] {}
        at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594) ~[?:?] {}
        at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183) ~[?:?] {}
Caused by: com.google.gson.stream.MalformedJsonException: Expected name at line 8 column 2 path $.
        at com.google.gson.stream.JsonReader.syntaxError(JsonReader.java:1559) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:505) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.stream.JsonReader.hasNext(JsonReader.java:414) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:184) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.Gson.fromJson(Gson.java:887) ~[server-1.15.2-extra.jar:?] {}
        at com.google.gson.Gson.fromJson(Gson.java:852) ~[server-1.15.2-extra.jar:?] {}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.prepareOverrides(LevellingConfigManager.kt:26) ~[?:5.1.2] {re:classloading}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.prepare(LevellingConfigManager.kt:38) ~[?:5.1.2] {re:classloading}
        at me.sargunvohra.mcmods.leveluphp.config.LevellingConfigManager.func_212854_a_(LevellingConfigManager.kt:14) ~[?:5.1.2] {re:classloading}
        at net.minecraft.client.resources.ReloadListener.func_215270_b(SourceFile:11) ~[?:?] {re:classloading}
        at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1700) ~[?:?] {}
        at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1692) ~[?:?] {}
        at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594) ~[?:?] {}
        at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183) ~[?:?] {}
←[m←[32m[19:00:09] [Server thread/INFO] [minecraft/MinecraftServer]: Preparing start region for dimension minecraft:overworld
←[m←[32m[19:00:09] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
←[m←[32m[19:00:09] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Preparing spawn area: 0%
←[m←[32m[19:00:10] [Server thread/INFO] [minecraft/LoggingChunkStatusListener]: Time elapsed: 861 ms
←[m←[32m[19:00:10] [Server thread/INFO] [minecraft/DedicatedServer]: Done (1.592s)! For help, type "help"
←[m←[32m[19:00:10] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM-1): All chunks are saved
←[m←[32m[19:00:10] [Server thread/INFO] [minecraft/ChunkManager]: ThreadedAnvilChunkStorage (DIM1): All chunks are saved
←[m←[32m[19:00:12] [User Authenticator #1/INFO] [minecraft/ServerLoginNetHandler]: UUID of player Rotzmaus is ff563aaf-aa6d-4684-8d22-595f0012e719
←[m←[32m[19:00:13] [Server thread/INFO] [ne.mi.co.AdvancementLoadFix/]: Using new advancement loading for net.minecraft.advancements.PlayerAdvancements@2ed2a755
←[m←[33m[19:00:13] [Server thread/WARN] [minecraft/NetworkSystem]: Failed to handle packet for /81.217.60.65:60788
java.lang.RuntimeException: Why did the advancements not load yet?!
        at net.minecraftforge.common.AdvancementLoadFix.loadVisibility(AdvancementLoadFix.java:51) ~[?:?] {re:classloading}
        at net.minecraft.advancements.PlayerAdvancements.func_192740_f(PlayerAdvancements.java:157) ~[?:?] {re:classloading}
        at net.minecraft.advancements.PlayerAdvancements.<init>(PlayerAdvancements.java:65) ~[?:?] {re:classloading}
        at net.minecraft.server.management.PlayerList.func_192054_h(PlayerList.java:743) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
        at net.minecraft.entity.player.ServerPlayerEntity.<init>(ServerPlayerEntity.java:164) ~[?:?] {re:classloading,pl:accesstransformer:B}
        at net.minecraft.server.management.PlayerList.func_148545_a(PlayerList.java:382) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
        at net.minecraft.network.login.ServerLoginNetHandler.func_147326_c(ServerLoginNetHandler.java:116) ~[?:?] {re:classloading}
        at net.minecraft.network.login.ServerLoginNetHandler.func_73660_a(ServerLoginNetHandler.java:63) ~[?:?] {re:classloading}
        at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:224) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
        at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:135) [?:?] {re:classloading,pl:runtimedistcleaner:A}
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:866) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:330) [?:?] {re:classloading,pl:accesstransformer:B}
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:784) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:637) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
        at java.lang.Thread.run(Thread.java:834) [?:?] {}
←[m←[32m[19:00:13] [Server thread/INFO] [minecraft/ServerLoginNetHandler]: com.mojang.authlib.GameProfile@8ffb5e7[id=ff563aaf-aa6d-4684-8d22-595f0012e719,name=Rotzmaus,properties={textures=[com.mojang.authlib.properties.Property@3cd1fdf1]},legacy=false] (/81.217.60.65:60788) lost connection: Internal server error