There are many reasons why you can't use a card. For example, insufficient quantity will lead to unusable; If the credit line is sufficient, there may be a problem with the merchant's credit card network or improper operation. You can try again with another merchant. It is also possible that the merchant's POS machine does not support this credit card in your hand. In addition, abnormal card status will also affect the use. You can call the credit card customer service hotline to check whether the card status is normal. Sometimes improper card swiping will lead to the card being locked, or it will be locked if you enter the wrong password several times in a row. Customer service can help you unlock it. If there is no problem in the query, it may be that the chip or magnetic stripe is damaged, and the chip is durable, and it is broken after rarely using it once. Ensure that the card cannot be used due to damage. Customer service can change your card. After receiving the new card, you can continue to use it by reactivating it.