I can't see photos anymore that i allready imported in Lightroom

Lightroom (Lr icon) or Lightroom Classic (LrC icon)? What version NUMBER? (We need the version NUMBER and not words like "latest" or "Up-to-date".)

Please be specific and tell us where you are looking that you can't see the photos. Please show us a screen capture of the entire Lightroom window when you can't see the photos, by using the "Insert Photos" icon to include the screen capture into your reply.