Your MyPANEL, FTP and MySQL password are all one and the same.

If you have uploaded a third-party PHP script or program that connects to your database, and this was uploaded before the password change, then the 'config.php', or 'configuration.php' file for the script will now need to be updated with your new password also, or you will receive database connectivity problems.

Such files can simply be opened with a text editor, the password can then be updated in the file to your new password, and then resaved back to your filespace.

This should then correct your database connectivity issue.