Hello Glenn! To help you with this question we need a little bit more information, please create a ticket here https://cloudlinux.zendesk.com/hc/en-us/requests/new and technical experts will help you asap.
If you have any other questions, feel free to ask here.
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Thanks for reply Sergey. Can you tell me how mod_security should be configured in plesk? Detect or Block?

I was originally told it Plesk mod_security was supposed to be set to Detection only but that was almost two years ago.

I prefer to avoid using tech support if I don't really need to. Your support is great but it's time consuming for both of us

Hello Glenn! It should work in block mode to provide protection. Otherwise RBL, CVE rules and so on will not work and protection will be limited only by agent functionality. If you have any other questions, feel free to ask here.
Thank you for contacting us.