Re: The cheat TestingCheatsEnabled true doesn't seem to work in The Sims 4.

I have just tested the cheat "testingcheats true" and "testingcheats false" in my game with and without mods/CC and the cheats work fine.

Cause in your game could be an outdated mod or CC if you use any. This can happen when a new patch is installed. If you use mods/CC deactivate them in your game settings and then try the cheats again. If it still doesn't work, open Origin and repair your game.