cpanel mysqli_connect(): (28000/1045): Access denied for user 'username'@'localhost' (using password: YES)

If you're trying to log into PhpMyAdmin on cPanel and come across that error, simply go to your webhost and reset your password for cPanel. That will update your FTP, MySQL passwords as-well and will fix the issue. If you are the reseller and owner of WHM, simply go to list accounts and update the password for the account in question. That will fix the issue.