I haven't heard of this happening with Sims 3 before, but with Sims 4 I have. I'm not sure what the cause of the issue is, but here a few tips to try:
1. Deactivate Origin in Game -- Open Origin, Select Origin > Application Settings > Origin In Game and click the on/off switch to disable Origin In Game.
2. Quit fully out of game, and restart the computer then get back into game.
3. Some programs may interfere with being able to use the cheat console. A couple known programs are called:
Gyazo - Screen Capture program that may use the same key combo as the Sims games. - If you have this program it may be best to uninstall it.
Skitch - Screenshot and photo editor for Mac that uses the same key combo as the Sims games. If you have this program, it's best to uninstall it or disable it.
Check to see that you don't have any other app/programs that use the same key combination Ctrl-Shift-C.
4. Sims 3 Factory Reset (HowTo)
http://www.carls-sims-4-guide.com/forum/index.php/topic,20732.msg401814.html#msg401814