Hi, this has definitely been working just fine. but today (before I upgraded – last time was around September 2015 – though there have been WordPress upgrades between) I checked and no calendars displaying on the front end.
Cleared my cache and tried a couple of different browsers.
I have now gone on and updated Booking System PRO to latest version and still same issue. The server environment check list looks fine.
Have a look at this page, it used to load the calendar here.