The Sims 4 (Modded) | Cheats don't work with error 'unable to execute command'

@PresumedCoast. You need to load a lot before entering the cheats: choose a household and go into live mode. Then enter:

testingcheats true

to unlock some cheats. 

Or:

motherlode

to get money, without needing to enable testingcheats first 

The cheats will not work if you go directly to build mode when starting the game. After having loaded a household once, you can go back to Manage World if you want. 

Use cheats with care.