Re: Can no longer save, manage worlds, or use build mode.
@lucindapowell12 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; if the folder copies instead of moving, or you get an error when trying to move it, stop here and let me know.
Otherwise, 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 let me know what problems, if any, are still present.