I am having the same issue.  When I go to "latest protection".  It starts a download, then says installing, then closes and restarts.  If I go back to latest protection, the process repeats.  I am on version 17.8.1121.  I have tried reinstalling and repairing windows.  SFC reports no integrity violations.  Windows is up to date. Windows 11 23H2 Build 22631.4249