Online shopping - "couldn't process your payment"

 I am trying to purchase a phone upgrade and have added my selection to my cart. At checkout I get the message "We couldn't process your payment" as shown in the attached photo.

This is a confirmed issue with T-Mobile.

• I have made purchases with this card just prior to and after making the purchase attempt from T-Mobile. Attempts by both web and via the app give the same message
• My card has no holds, denied charges, and over 20k in available credit. All confirmed by calling my Capital One Venture X card support
• Capital One showed that an attempt was made by T-Mobile for $0 though the due amount shown at checkout is $120. Clearly a disconnect between the checkout page and the charge requested by T-Mobile

Yes, I can use a different card though the Venture X offers Phone insurance if the phones are purchased with it. Also, in looking at posts from a year ago similar issues were reported with different cards. I called T-mobile support and they offered to try to process with a representative, however that would cancel some of the benefits of purchasing online as promoted by T-Mobile. example - $35 fee cancelation per phone upgraded and the way the phone credit is distributed to be applied completely to the upgraded phone cost.