Found this thread when I had the same problem, thanks for the tip.

Yes open the Qatar app then the home tab should show "Your flight QRXX departs tomorrow" below that there is a maroon box with icon of phone/QR code. Tap that then the add to wallet option comes up. However you also need to repeat the same thing for all of your connecting flights, do this in the home tab by swiping left on the flight info card below the maroon box. This is different from other airlines that usually add all the passes to wallet in one step.