Ok so ive been using testingcheatsenabled true for like, ever and it stopped working just now. I did download some new content but i played a few times with that content running and it worked. The game froze recently (it happens sometimes). i could not use any buttons or close the window but the music was still playing. I logged out then back in and ever since then, some cheats work but others, like testingcheatsenabled true and buydebug and alwaysallowbuildbuy on are all "unknown cheats."
this happened to me too. when you turned off the game improperly, the cheats that use on/off were stuck. all you have to do is type in "testingcheatsenabled false" because it is a base cheat and this will reset them. then type in your cheats as usual and everything should work just fine.