If you paid late and your server was turned off it is possible that your MySQL server did not start properly when you booted back up. In this case your web server (hosting phpmyadmin) is running but your database server may not be.

Log into your server via ssh and try restarting the MySQL service:

service mysql restart

If the service fails to start let us know what error you see and check your logs in /var/log/mysql for additional details.