If CCB's credit card cannot be used in pos machines, please check the following contents: 1. Whether the POS system enables UnionPay card transactions; 2. Whether CCB's credit card has a chip; If there is a chip, please confirm whether POS supports downgrade transaction; 3. Whether CCB's credit card is within the validity period; 4. Whether the credit card balance of CCB is sufficient; If all the above are all right, please contact the credit card center to check the status of the card and replace it. Credit card reader is referred to as POS terminal for short. The terminal dials through the telephone line to send the information to the UnionPay platform. After the platform of UnionPay recognizes the relevant information, it will send the deduction information to the issuing bank, and the issuing bank will send the information back to the platform of UnionPay after confirming it. After confirmation by UnionPay, the processed information will be sent to the front-end terminal, and the terminal will print the documents after receiving the confirmation information. Mobile POS terminal, the same principle, its letter