Plutonium

Hi, recently whenever I tried to play t6 zombies I've been getting this error-

I haven't used GSC Studio since November 2020, nor do I have it in my files anymore so why is it just now giving me this error? It's probably a simple fix, but I wanted to post this on the forums before I screw up my game.

Am I allowed to use things like cheat engine or other things in SOLO custom zombie games? I don't plan on doing it in public lobbies. Hell, I don't even join them 9 times outta 10.