Originally Posted by
aisleorwindow
...
Only thing I can think of is that because it was extended, the system still showed the original expiration date from the initial booking.
Many similar reports, UA is tightening the extension process. Likely UA never intended to allow extending and existing FFC. It was nice while it lasted but these extension loopholes are disappearing. The find a bookable flight within the original expiration and than change flight as far out as possible and then cancel seems to work for some.
The incorrect date on the present extended FFCs is a pain.