The checkbox in-question here is a checkbox that is automatically inserted into the WordPress login form.

This plugin is founded on using standard WordPress API/hooks/filters. If you are using a custom login form that doesn't use these standards, then it's possible that the form doesn't fire the necessary WordPress hook that allows us to insert the checkbox.

If this is the case, you have 2 options:

  1. Turn off the GASP option (Bot Protection) within the Login Guard module since your custom login form doesn't support it; or
  2. Don't use a custom login plugin/theme or use one that supports standard WordPress login hooks.

The other possibility is that your browser may not be setup to support Javascript. Your options are:

  1. enable Javascript on the browser; or
  2. disable the GASP option.

Read here on how to disable GASP option.

For further reading on GASP protection for WordPress login, read the blog article here.