restricted due to a security rule

I installed subscribe to comments and translated it littlebit.

When saving changes i got page:

The page you are trying to access is restricted due to a security rule.

If you believe the security rule is affecting the normal operation of your website, contact your host support team and provide detailed instructions how to recreate this error.
They will be able to assist you with rectifying the problem and adjusting the security configuration if needed.

Might you have idea what′s wrong? I′m using iThemesSecurity.

https://www.ads-software.com/plugins/subscribe-to-comments/