not working for html content

Hi, thanks for using Force Login!

My response to the following support thread applies here as well:
https://ww.wp.xz.cn/support/topic/documents-not-protected/

The plugin can’t force a redirect from static files (.pdf, .doc, .jpg, .html…etc). No PHP or WordPress script runs prior to loading static files; the server just loads the file.

If you want to restrict access to the uploaded media files, you’ll have to configure your server to pass or “proxy” all requests to the uploads folder through a php script that can check if the user is logged-in.

Check out the following URL for an example of how to do this:
http://wordpress.stackexchange.com/a/37743/48165