According to relevant information from Nongfu Financial Network, the reasons why Marriott prompted that the credit card number is invalid are as follows:

1. The user did not activate the credit card after receiving it.

2. The credit card is damaged, such as the entry is worn. If the credit card has been used for too long, it is normal for it to be degaussed and damaged.

3. The account status is abnormal. For example, if a credit card account is stolen and the risk level is too high, it will be easily controlled by the bank.

4. The credit card has expired. As we all know, credit cards have a certain validity period. If the user uses the credit card after the validity period without changing the card, it will not be able to be used.

5. The credit card is seriously overdue. For example, in the process of using a credit card, a user is often overdue and never pays back the overdue amount. In addition, the bank has been unable to contact the user. This will not only affect the user's personal credit score, but may also prevent the user from using the credit card again.