If you can’t add cash to the cash app card then perhaps it was due to a card number mistake, an expired debit/credit card, or insufficient funds or you have accessed the Cash app. If your credit or debit card details are accurate and your card hasn't expired then you have to get in touch with credit or bank to have the problem resolved.

Why can’t I add Cash to my Cash App from my debit card?
This error usually happens due to blocked or declined cards. Many people accidentally add the wrong card or don't check the status. If you also make some mistake, the app won't let you transfer the money. You'll receive the error message and need to contact your card issuer in such a case.
Cash App Won't Let Me Add Money from Debit Card
This is because there are chances that you are using a blocked or expired cash card for this purpose. The cash card that is issued to you after you got verified has to be an inactive state for proper functioning. If anything such as blocking or expiration occurs, it will hinder the transaction. In that case, contact the card issuer.