Booking Sleep Cabin
These sites have been set up to service their own airline members and when they join an alliance or merge with another airline, the question to ask is who is now operating/ running the software. As in the case of Virgin Atlantic the software is run by Delta, which when you cannot book a return flight, doesn’t tell you why, just phone customer service on an estimated 4hr wait!
Maybe Air France is in charge. A work around may be to join Flying Blue then unsubscribe after your flight.