Hi @Kmc6599 and welcome to the Seller Community!
When you manually enter a card, the information is cross-checked with the customer's bank or card issuer for approval.
If one of the pieces of information doesn't match what the bank has on file like the billing zip code or it's missing a digit, it won't be able to verify the card being used.
Also, do you know what kind of card it is? Wanting to make sure it's an accepted card brand.
Ashley C
Community Moderator, Square
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