I had an eventful morning trying to use two FFCs. One wasn't showing up in my account and wasn't showing up in searches even though I had email confirmation and the rep could see it. The problem is her solution was to convert the broken FFC to an ETC (without even asking me) but because she did that I wasn't able to use it with the working FFC since they can't be combined. One hour and one supervisor later and they ended up converting both to ETCs where I was finally able to apply them to the flight I was trying to purchase.