403 error

When i ban a spammer using their ip address and save using this plugin I get this on front or back end of site thereafter

Forbidden
You don’t have permission to access /wp-admin/plugins.php on this server.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

This is the 2nd time it’s happened. How do i fix- so annoying that it takes down my site?

https://wordpress.org/plugins/better-wp-security/