The game doesn't start anymore(after downloading the mod). I tried unsubbing from the mod but that didn't fix it either. I then verified the game files and it found 3 files missing which it redownloaded but the game still doesn't start. How do I find the stack trace?

Hello, how did you open the game?

If you opened the game through Steam, you did not install the modification correctly, you need to run the Plusic API so that the modification is embedded in the game.

If you open the game after deleting the modification, most likely this is due to a game error, because I saw a similar error on the forum before:
Forum link[www.ageofcivilizationsgame.com]
Lukasz ask link

Ok it seems that i had forgotten to install the plusic api so I did that then I started the game from the loader. But it said that my java was outdated on the console so I updated it. Now it works flawlessly. Thank you.

Plusic Api didn't work because Lukasz changed the jar file's name I think. It was game.jar for me so I changed the name to aoh3.jar but I'm getting another error now.

Error: Could not find or load main class aoc.kingdoms.lukasz.jakowski.desktop.DesktopLauncher

I have a suspicion that he changed the name of the packages, thanks for the information, I'll check a little later.