Seat map and seat selection not available
I'm flying IAD-JNB-CPT-IAD with a layover in Dubai both ways. I was able to select my Seats on 3 of the 4 legs. The leg from CPT to Dxb I can't select my seat. It gives me a message "Sorry technical error. Seat selection is no longer available for this flight". It doesn't even show me the seat map. It's just blank.
I can't imagine the flight is over sold already because the flight isn't until September 4th. I have been trying to select my seat for this flight for 2 weeks. Any idea what this means?