@KarenJay As a test, please try playing in a clean user folder. Move the entire Sims 4 folder out of Documents > Electronic Arts and onto your desktop, and when you launch the game, a clean folder will spawn with no content. (Your saves and other content will be intact in the folder you moved but temporarily not read by the game.) Don't add anything to the new folder yet; just start a new save and see whether CAS works.
If that doesn't help, let me know whether your computer runs Windows or macOS. If Windows, please run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
