sims 3 pop up error

so i keep having this problem of when i open my Sims 3 game it has a pop-up saying '  there is a serious issue with / file it is recommended you restart the application'. it happens with old saves and new ones. i even deleted all my saves in case one was causing the problem and it still happens. i deleted and reinstalled my game and it was fine the first time i played it then when i went to play it again the pop-up happened again. i have tried to get rid of one drive for my Sims 3 file but it won't UN sync and i don't know what is causing the issue i just want to play my game ☹️