I am not entirely sure if this will help, but here are a few troubleshooting tips to try:
1. Make sure the cheat console is actually coming up or not. It's a dark Blue box that comes up in the upper left hand corner of the screen and may be hard to see.
When you're in Live mode, while on pause, press ctrl+shift+c (screen will go dim and text line appears at top)
Type cheat: most commonly, testingCheatsenabled True (no underscore)
Hit enter and screen will go back to normal.
To de-activate cheat mode, do same, except, testingCheatsenabled False
If you make an error or decide to not activate a cheat, delete any text from the line and hit enter. That will return screen to active play.
2. If your computer was previously set to use ctrl-shift-c to access another function you'll have to find out what and change it. For example if a game was set up previously to use ctrl-shift-c.
-- To do this:
Press Ctrl + Shift + C when out of game to see what opens. Then close it and find the .exe file for it, right click, choose Properties, then change the "Shortcut" to something else.
3. Something that has worked for others: Try different key combo such as: Ctrl key on the left side along with the Shift key on right side with the C key all together. This should work in both Sims 3 and 4
4. If you're playing the game through Origin, try repairing the game:
Repair Game - You can repair packs and the base game separately. Right-click on whatever pack you want to and select Repair Game. Then go back to Base Game, and right-click on it and select Repair Game.
5. Try running a Clean Boot as this will help with stopping any other programs from interfering.
http://help.ea.com/en/article/how-to-clean-boot-your-pc/