Symptoms

If PhpMyAdmin is failing to load or is continuously redirecting to itself, it may be possible that the "mysql" database is corrupted or needs to be upgraded.

Description 

It may be possible that the "mysql" database cannot be accessed while accessing PhpMyAdmin. If you check the cPanel error log (/usr/local/cpanel/logs/error_log) you may see this information being reported:

Cpanel::Exception::Database::Error/(XID 6pga43) The system received an error from 
the “MySQL” database “mysql”: 
1805 (Column count of mysql.proc is wrong. 
Expected 21, found 20. The table is probably corrupted)

Workaround

To resolve this, you will need to perform a mysql_upgrade. It is recommended to first take a backup of your databases before doing this. If you do not have any database backups, and are not sure how to take a backup, you can use the command below:

mysqldump --all-databases | bzip2 -c > /home/databasebackup.sql.bz2

Once you have taken a backup of your databases, you can use the command below to ensure all database tables are checked and upgraded for the latest version

mysql_upgrade

Once this is complete, PhpMyAdmin should be able to load once again.