DaemonUmbra

Show the screen that's saying this?

Try a more recent version of Forge Hold up, yeah that's a 1.14.4 log... erm. Post launcher_log.txt then

Don't register things conditionally, always register everything

https://adoptopenjdk.net/index.html

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Please don't hijack threads. (Split into its own thread) Try Java 8

The in-game config menu hasn't been updated yet, you should still be able to edit the config files manually before starting your game

Unless you've made your own you'll only see the generated ones. Besides that the generated ones all use LaunchTesting and are chock full of command line arguments

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No

You should be opening the Run Configuration list and selecting one of the runs that genEclipseRuns generated (Note: These will not appear directly under the run button until you've used each one once, but they will appear in the complete list)

Were there any errors when you ran the Forge installer?

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How are you starting the game?

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Delete your config folder

Try using a Java 8 JDK

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