Phaewalker Do you still need help? If so, this sounds like it might be antivirus-related. Please see the first post of this master thread for help:
[CURRENT ISSUE] Anti-Virus blocking User Folder (Screenshots/Gallery/Mods..) | EA Forums - 11778999
Other suggestions are here:
[CURRENT ISSUE] Sims 4 Unable to Start, Game Data Missing or Damaged | EA Forums - 11819181
As for why this started happening now, it's possible your antivirus updated, or maybe you changed which executable Sims 4 is using (Memory Boost vs. not, DX11 vs. DX9) and the antivirus is blocking actions from the new .exe where it was fine with the previous one.