I get the message "You must check that box to say you’re not a bot" but there's no check box on my WordPress login form

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 more about GASP option here.

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

Is there any other solution?

You can trying out our Antibot Detection System. They're the newer, better way to protect the forms.
This completely removes the need for login form CAPTCHAs, and Shield’s own GASP “I’m a human” checkbox. We’re passively testing a visitor’s status (no direct interaction required from the visitor), and we build their Bot Score and allow or deny the request.
This system is best explained in our release blog posts here.