client denied by server configuration

[GlowHost-Sara]

If some specific IP's are causing load, you can ban those IP's via cPanel deny manager as you have done. Usually this process won't cause any "client denied by server configuration" errors. Did you accidentally put your IP also there ? You can check your IP via this page:

https://glowhost.com/support/what-is-my-ip/

Blocked IP's won't be able to connect to the site in future, however, if you remove the rules from .htaccess then they can access it once again.

If you still face any issues, I would suggest you open a support ticket so that we can dig deeper into the issue and fix it permanently.