CAS is a white screen

JayBirdXXX  As a test, please move the entire Sims 4 folder out of Documents > Electronic Arts and onto your desktop.  When you launch the game, a clean folder will spawn with no content.  (Your saves and other user content will be intact in the folder you've moved but temporarily not read by the game.)  Don't add anything to this new folder yet; just start a new save and see whether CAS works.

If you get another white screen, please provide a dxdiag.  Hit Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop.  From there, you can attach it to a reply using the camera (Insert Media) icon with the other formatting options.