This is always a mess IME. Had a similar problem with a booking on 125- stock but involved BA and AA and ended up in a loop between BA and AA websites with things like seat selection and BP generation. At one point I couldn't get a BP because the app said the sector (which was in the middle of the itinerary) was unticketed - which was, of course, untrue, but it still resulted in a call to the TA to check they had issued the ticket correctly.

It's an area that OW airlines seem to really need to improve on.