1. Confirm card status: Before using a credit card, you need to confirm whether the card status is normal, such as whether it has been reported lost, frozen or expired. If there is a problem with the card status, you need to contact the bank customer service for handling.

2. Check the consumption limit: Some credit cards have restrictions on consumption, such as single consumption limit and daily consumption limit. If your consumption exceeds the limit, you may not be able to use it normally.

3. Check the network connection: If you use mobile payment or other online payment methods, you need to ensure the normal and stable network connection of your mobile phone or computer to ensure the smooth payment process.

4. Contact the customer service of the bank: If the above methods fail to solve the problem, I suggest you contact the customer service of China Merchants Bank for more detailed and professional help and guidance.