My Downloaded Sims game keeps saying it isn’t downloaded

avocado_naii  Does this happen with no mods or custom content at all?  Please test if you haven't already.  You don't need to save your progress.

If it does happen, please post a screenshot of the error.  Please also look for a new lastexception file in Documents > Electronic Arts > The Sims 4.  It would be best to delete your current ones first, then see whether the game creates a new one.  If it does, open the file, delete the first line of text, and you should be able to attach it to a reply here.