Pixelmon Wont work

[Evin]

I keep trying to start up pixelmon and this keeps happening

 

---- Minecraft Crash Report ----

WARNING: coremods are present:
  LoadingPlugin (ResourceLoader-MC1.12.1-1.5.3.jar)
Contact their authors BEFORE contacting forge

// Surprise! Haha. Well, this is awkward.

Time: 11/25/20 12:19 PM
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Pixelmon (pixelmon)
Caused by: java.lang.NoSuchMethodError: net.minecraftforge.fml.relauncher.ReflectionHelper.setPrivateValue(Ljava/lang/Class;Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/String;Ljava/lang/String;)V
    at com.pixelmonmod.pixelmon.comm.PacketRegistry.replaceNetworkCheck(PacketRegistry.java:364)
    at com.pixelmonmod.pixelmon.Pixelmon.preInit(Pixelmon.java:138)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:611)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
    at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
    at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
    at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
    at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
    at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
    at com.google.common.eventbus.EventBus.post(EventBus.java:217)
    at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:253)
    at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:231)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
    at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
    at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
    at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
    at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
    at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
    at com.google.common.eventbus.EventBus.post(EventBus.java:217)
    at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:148)
    at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:604)
    at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:266)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:466)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:377)
    at net.minecraft.client.main.Main.main(SourceFile:123)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
    Minecraft Version: 1.12.2
    Operating System: Windows 10 (amd64) version 10.0
    Java Version: 1.8.0_51, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 399470320 bytes (380 MB) / 805306368 bytes (768 MB) up to 2147483648 bytes (2048 MB)
    JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    FML: MCP 9.42 Powered by Forge 14.23.0.2486 7 mods loaded, 7 mods active
    States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored

    | State | ID                | Version      | Source                              | Signature                                |
    |:----- |:----------------- |:------------ |:----------------------------------- |:---------------------------------------- |
    | UCH   | minecraft         | 1.12.2       | minecraft.jar                       | None                                     |
    | UCH   | mcp               | 9.42         | minecraft.jar                       | None                                     |
    | UCH   | FML               | 8.0.99.99    | forge-1.12.2-14.23.0.2486.jar       | e3c3d50c7c986df74c645c0ac54639741c90a557 |
    | UCH   | forge             | 14.23.0.2486 | forge-1.12.2-14.23.0.2486.jar       | e3c3d50c7c986df74c645c0ac54639741c90a557 |
    | UCH   | mercurius_updater | 1.0          | MercuriusUpdater-1.12.2.jar         | None                                     |
    | UCE   | pixelmon          | 8.1.2        | Pixelmon-1.12.2-8.1.2-universal.jar | None                                     |
    | UCH   | resourceloader    | 1.5.3        | ResourceLoader-MC1.12.1-1.5.3.jar   | d72e0dd57935b3e9476212aea0c0df352dd76291 |

    Loaded coremods (and transformers): 
LoadingPlugin (ResourceLoader-MC1.12.1-1.5.3.jar)
  lumien.resourceloader.asm.ClassTransformer
    GL info: ' Vendor: 'ATI Technologies Inc.' Version: '4.6.13587 Compatibility Profile Context 19.40.48 26.20.14048.2' Renderer: 'AMD Radeon(TM) Vega 3 Graphics'

[LexManos]

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.