Re: CAS background wont change.
@iSnoopy2001 Is it possible you put this background in a different subfolder? Try moving your entire Mods folder to the desktop, as as test. Start a new save to see whether the background is still there.
If it is, please confirm that the Mods folder you moved is the one from the Sims 4 user data folder the game is actually using. This is easy: just check the last modified date on config.log inside the folder. Its time and date should match the last time you launched the game, as in, a few minutes before when you opened TS4 to test.