If the issue you're having occured after the installation of a mod, please disable the mod and try to reproduce the error.

If the mod prevents you from launching the game, go to %UserProfile%\Zomboid\Mods and delete the loaded.txt file.

If you installed the mod directly into the Project Zomboid installation directory (%ProgramFiles(x86)%\Steam\steamapps\common\ProjectZomboid), please manually delete the contents of the ProjectZomboid folder and reinstall the game through Steam. Steam's uninstall protocol will not remove the files for you.