How to fix Illegal Use 115 GameGuard Error

https://gameguardfaq.nprotect.com/eng/con_03.html

open task manager (alt+control+del or control+esc+shift) - > Details - > Find gamemon.des and gamemon64.des and right click end task
(others state crashing all gameguard/nprotect helps)

Next close undecember or crash it. If its stuck closing . Right click on it on steam go to properties - > local files - > Browse and Run it.

Done

Enjoy Undecember.