Most of the credit cards have a spending limit over a 15-day period. If you reach this limit, the payments with this credit card will be refused even if your account balance is positive.
- try again in a few days (your limit will be reconfigured);
- ask your bank to increase your limit;
- use temporarily another card in case you own one.
If the problem persists, please choose another payment method available on the site: check or transfer.