Is there an active Security plugin for the site?
I got this “error” text when the plugin ban the IP where i try to view the site. Better WP security is set up on the site, I added my email address and when I try to open from a banned IP PC, I got email with “Site lockout notification” and this error on browser.
So I guess, check the security plugin. Maybe your IP is in a blacklist somewhere and that is the reason of the error text.
I hope this info will be helpful for you.
