You are getting below error while accessing your cPanel site.
Internal Server Error 500 No response from subprocess (whostmgr (cpanel)) with exit signal: 0 cpsrvd/18.104.22.168 Server at server.itsiti.com
1. If you have the operating system level access, you can execute below command to restart the cPanel process else forward the issue to your website service provider to solve.
service cpanel restart