Logging in shows a dashboard asking you to implement it on your site.
That's not what I expect from a "demo" of a captcha.
A recommendation would be; please use mcaptcha on the mcaptcha account sign up page at the least. It'd then provide an instant user UX demo which is one of the major pains of captchas.
Or at least provide a link to the widget[1] for UX demo, where inspecting networks calls also shows the api calls in action
This is listed on the sign in page [1], just not very visible.
> user: aaronsw password: password
[1]: https://demo.mcaptcha.org/login