The error code GENERIC_DECLINE is returned when the card issuer declines the payment for an unknown reason. This error is usually out of Square’s control and is decided by the customer’s bank. The fact that the payment eventually succeeded suggests that the issue was temporary and was resolved by the bank.
It’s also important to note that each payment request should have a unique idempotency key. If you use the same idempotency key for different payment requests, you might get an error indicating that you used the idempotency key previously.
If the issue persists, it might be a good idea for the customer to contact their bank to understand why the transactions were initially declined.
This answer was reviewed by @Bryan-Square.