Ajax Appointments+ Calendar disappears/doesn't show

I'm looking to get the Ajax-ness up and running with the appointments+ plugin and am aware that it is a beta functionality (however it seems to have been in that state for many years according to other posts on this forum), but it isn't working for me at all on this page.
Here is my shortcode setup:
What happens is the Services dropdown appears, but when you click on the Show available times button everything disappears and no calendar shows. I have tried this with the default 2016 theme (and all plugins turned off) and still nothing happens when the button is clicked.

Has anyone else had any luck with this?

Thanks in advance,