When a7 appears on the POS machine, it does not mean that the card is blocked. "A7" means that the transaction processing failed.

The reasons for the failure of credit card swiping are as follows:

1. The credit card is not activated after receiving the card.

2. The credit card transaction password was entered incorrectly.

3. The line at the POS machine is unstable when swiping cards.

4. The consumption amount is greater than the available limit of the credit card, resulting in failure to swipe the card.

5. The cardholder's frequent card swiping and abnormal consumption habits in a short period of time on the POS machine made the card issuer think that the user was committing cash-out behavior and made a decision to ban the card swiping.