Who did you book through?
FWIW, I booked three tickets from AMS-HKG-MEL using QFF points the other day. My QFF number was linked correctly and the ticket was on 081 stock.
As a OWS (SG), I was able to select extra legroom seats at 60A on the A359 as expected, while my dad who's OWR (PS) could select a regular seat (60C). However, I couldn't select a seat for dad's partner who's without status (she got the same error as you), so I've added the trip to my Cathay account (without changing the FF number) in the hope of getting her 60B on both legs by checking in at T-48h. Despite adding it, the QFF numbers have remained on the booking.