My 2 x $100 credits posted after a few days.

FYI for those like me who weren't aware of this caveat: funds in the Travel Bank are only valid for reservations with only United and/or United Express flights. If your reservation contains any segment of another airline, you will not be able to apply anything from your travel bank as a form of payment. At least that's what the United rep told me.

Also, you cannot pay with both travel bank and flight certificates in the same booking. (I think most of us know this already.)