trying to buy united TB using my biz plat annual travel credit and getting the error message below.

any workarounds? is not an amex issue as charge goes thru, though is immediately followed by a credit.

1. i tried adding to my account making it a saved card and still nothing.
2. tried gifting it from P2 and still no go.
3. attempted purchase on multiple devices
4. ditto on multiple browsers
5. also on different days