First thing you’ll neet to do is to check the error logs.(Generally its here /usr/local/apache/logs/error_log). You will probably see errors referencing permission errors writing to your session directory.
If no success….
# vi /usr/local/cpanel/3rdparty/etc/phpmyadmin/php.ini
and change the values for
session.save_handler = sqlite
session.save_path = /var/cpanel/userhomes/cpanelphpmyadmin/sessions/
session.save_handler = files
session.save_path = /tmp
after saving the file, restart apache.
If after upgrade its reverting back, or you don’t want to change the session.save_path in php.ini for phpmyadmin
# mkdir -p /var/cpanel/userhomes/cpanelphpmyadmin/sessions
# chmod 1777 /var/cpanel/userhomes/cpanelphpmyadmin/sessions
and restart the apache service.
This should resolve the issue.