Well something appears to be working because deleting/deactivating wp-admin BulletProof Mode did something. I’ll use this LiteSpeed server case as an example. LiteSpeed has added support for most of the Apache directives, but not the SetEnv directive (fully anyway – some things are supported). So what that means in the case of LiteSpeed servers is that if you try to use htaccess code like this for example: SetEnvIf Request_URI "/bulletproof-security/403.php$" whitelist
the LiteSpeed server ignores the SetEnvIf Apache directive and the result is the code has no effect whatsoever since it is not supported by LiteSpeed servers/is ignored. Or in other words, there is no equivalent LiteSpeed handling/processing done for that Apache directive.
So my best guess is that some Apache directives are supported on your Windows IIS server and some are not or it is also possible to instruct the server to intentionally ignore Apache directives. ie if the ErrorDocument directive is found in htaccess code/files then ignore it and do not handle/process that directive.
Since this is a server issue and your website relies on what the server does and does not allow then there is only one approach to take – find out what the server does and does not allow. htaccess files are distributed server configuration files that instruct your server to do something, BUT if your server says “i am not going to do that” or “i cannot do that” then the only approach is – find out what the server does and does not allow. ??