Problem with Version 10.4.6

Dear Sir or Madam!
Since the update to version 10.4.6, I receive for pages to be displayed in the backend: “The requested page is missing a valid site configuration” and in the frontend: "Page Not Found The page did not exist or was inaccessible. Reason: The requested page does not exist " The “View Webpage”-button does not respond at all. Can you help me?
Regards, Strawk