I (unwisely) tried to purchase an Icelandair ticket via the Chase travel portal. I would get a reservation number, go buy seats on Icelandair's website, and a few days later the entire reservation would vanish into the ether. Rinse and repeat 3x.
I can't remember the exact verbiage, but basically tickets can be "reserved" and "booked". One means the ticket is allocated, and one means the ticket is actually paid for. I eventually sat on the phone with an executive support person as they booked the ticket and got it all the way through. It turns out Chase reserves a ticket on an airline but as an SLA of ~3 days to actually pay for the ticket. Icelandair's requires a ticket to be paid with in 24 hours, so it was timing out.