I am unable to add my Capital One debit card to the Apple Pay account

Please contact Capital One support team and find out why they’ve hit a snag. Banks approve or decline their debit card being added to an electronic wallet. Generally, you can call the phone number printed on the back of the debit card and reach their support team.

Do you use a VPN? Do you have excellent WiFi and cellular connectivity? Have your tried using both WiFi and cellular?

Are you trying to add the card via the Capital One app?