1. Check the credit card status: First, make sure that your credit card account has not been frozen, lost or expired. You can confirm the status of your credit card by contacting the customer service department of the issuing bank or logging into the online banking system.

2. Check the magnetic stripe or chip of the credit card: If you pay with a credit card reader, make sure that the magnetic stripe of the credit card is not damaged or scratched. If the credit card has a chip, please make sure that the chip is not damaged or dirty. Wipe the chip gently with a soft cloth to ensure the surface of the chip is clean.

3. Clean the credit card slot: If the card is inserted for payment, check whether the credit card slot is blocked by dust or sundries. Carefully clean the slot with a clean soft cloth or cotton swab and ensure that the slot is dry.

4. Check password input: If you encounter problems when using credit card for online payment or cash withdrawal, please ensure that the password or verification code entered is correct. Check whether the keyboard works normally to avoid typing mistakes.

5. Contact the issuing bank: If the above steps can't solve the problem, I suggest you contact the issuing bank of the credit card directly, reflect the problem to them and ask for help. The customer service department of the bank will provide you with more detailed guidance and may need to further check your account or card.