I have a round trip ticket HKG-DOH-CMN ticketed by QR and operated by both QR (HKG-DOH) and AT (DOH-CMN). A PNR and a ticket number were given by QR. However, they are not recognized by the website of AT when I tried to choose a seat on the AT legs. I called both QR and AT but they could not help. Any recourse?

Also, when transiting via DOH, do I have to recheck my checked bags and perform security check again?