1. If the credit card account is overdue, the bank can freeze the account to prevent the overdue amount from increasing.

2. If the bank makes internal adjustments to some accounts, such as modifying the credit conditions of the account or restricting some functions of the account, the available credit limit of the card will also be 0.

3. In order to standardize the development of banking business, the relevant regulatory authorities may also require banks to restrict some accounts, resulting in a credit card available limit of 0.