.... New ticket numbers but same PNR
That;s the problem.
You used FFC as the starting point and re
booked the same flight and therefore maintained the original PNR. No residual in that case.
If you had changed to a different flight, did another cancel and then rebooked the original flight - keeps the original PNR but then the residual FFC is generated
or (my preference)
you do a new booking (ignoring the FFC) and then at the end apply the FFC as a form of payment This creates a new PNR and a residual (original) FFC
From the thread's wiki
Originally Posted by wiki
If you want to extend an FFC, the most reliable process is
Best approach is by purchasing a new non-refundable (non-BE) itin, for same passengers as the FFC. Do not use change of flight, start a new booking without using the FFC.
When you get to the payment page, then use the FFC as a form of payment
Wait a bit over 24 hours and then cancel.
You then will receive, essentially instantaneous, a new FFC with an expiration 1 year from the booking date.
The new FFC must be used for a trip starting before the new expiration
Deviations may not be successful
This will not work for FFC from a partial flown trip.
This works for extending ETC also except the ETC with be converted to a FFC and locked to the named passenger.
There is no guarantee this process will work in the future