I'm going through the exact same thing right now. I have two credits that I can't use, and it appears it's because they were attached to SWUs. I spent an hour on the phone with EP desk, and finally got the SWUs reinstated (why is this so much harder than it used to be)? I was told that the SWUs stay attached to the tickets, which are flight credits upon cancellation of the reservation, and that upon using the flight credit the SWU then gets redeposited back. OK, whatever--so EP desk got my SWUs redeposited in real time, but I can't use either of the flight credits online (one is a currency purchase issue, the other says "you entered a refundable flight credit . . . " which seems nuts, as it wasn't a refundable fare, though what I paid should be refunded to travel credit. I'm going to write it all out to customer service, to have it all on the record, and then book and hold reservations, then call EP desk to get the credits applied to new travel . . . I guess. Trust me, though, I will not forget they are there, for about $1,800!