Originally Posted by KingCanute

If QR have said the ticket is invalid, and looking up the reservation in Manage Booking on the QR website also shows it as cancelled or non-existent, then unfortunately you do not have any seats to give up.

Have you tried making a new booking? If they haven't deducted any avios or cash and the seats are available again, then just go ahead and rebook, perhaps using a different payment method for the cash element or doing it over the phone