The reasons for "invalid card" may be as follows

First, the card status is abnormal, such as card degaussing, chip damage, etc.

Second, the card Transactions are not supported. For example, VISA single-logo cards/JCB single-logo cards do not support UnionPay transactions, nor do they support some online transactions.

Third, there is no problem with the card. The POS machine signal is not good and cannot be connected. Networks can also cause transactions to fail.

Fourth, IC chip credit cards, because UnionPay has closed the downgrade transaction function, if the cashier still operates the transaction by swiping the card instead of inserting the card, it will also become unusable

Fifth, some overseas website transactions do not support domestically issued credit cards, or do not support credit cards from China Construction Bank

If the poster has other questions, you can ask.