I also posted this in Github Issues https://github.com/MinecraftForge/MinecraftForge/issues/7476

 

Minecraft Version: 1.16.13

Forge Version: 1.16.3-forge-34.1.42 and 1.16.3-forge-34.1.10

Logs: https://gist.github.com/rakista112/2edbfd33c46cc7e94965f35d1ad62210

Steps to Reproduce:

1. Install 1.16.3-forge-34.1.42 and 1.16.3-forge-34.1.10 client
2. Click Play

Description of issue:
Right after clicking play, it outputs the linked log to the Development Console and displays the following error in the Game Output:

Error: Could not find or load main class 
Caused by: java.lang.ClassNotFoundException: 

The logs also write this every time I click Play.

[09:00:51 SEVERE]: Couldn't download resources
java.io.IOException: Server returned HTTP response code: 403 for URL: https://s3.amazonaws.com/Minecraft.Download/indexes/1.16.json
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1932)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1528)
	at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:224)
	at net.minecraft.launcher.updater.a.a(Unknown Source)
	at net.minecraft.launcher.updater.a.downloadResources(Unknown Source)
	at com.mojang.launcher.game.runner.AbstractGameRunner.downloadRequiredFiles(Unknown Source)
	at net.minecraft.launcher.game.a.downloadRequiredFiles(Unknown Source)
	at com.mojang.launcher.game.runner.AbstractGameRunner.playGame(Unknown Source)
	at net.minecraft.launcher.game.GameLaunchDispatcher$1.run(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:832)

[09:00:51 INFO]: Download job 'Resources' skipped as there are no files to download
[09:00:51 INFO]: Job 'Resources' finished successfully (took 0:00:00.000)

I can play normally without forge though.

Looking forward to hearing from you.

@diesieben07

Yes, I'm using the old launcher.

Okay. Is there a previous version for MC 1.16.3 that I could downgrade to that will work with forge for the old java launcher?

Okay, I'll use the new launcher. Thanks