Unable to connect the card to apple pay

I’m not sure how much you want me to explain, so the bottom line is three parties are involved in approving your card. Apple is not one of the three. Those involved are the issuing bank, Token Service Provider (TSP), and Payment Network Operator (Visa, Mastercard, American Express etc.). One or more of the three are Red flowing (sometimes called Red Path) your card, device and/or Apple ID. Again, Apple is not one of the three involved.

The only consumer contact of the three is your bank. Please contact the Apple Pay Support team at the bank. Generally, basic support staff at banks are unaware of the systems related to Apple Pay and card verification. You may need to ask for a supervisor and escalate the issue to the Apple Pay support team. But only your bank can contact the TSP and Payment Network Operator.

Have you received the terms and conditions and agreed to them?

What happened that the card is no longer in your Wallet app? What did the card issuer say when you called them?

Are you logged into your Apple ID account on both devices?

Do you use a VPN or ever had VPN or antivirus software on your iPhone?

What kind of card is it credit or debit card? What bank issued the card?