Hello,
probabaly you are deactivated the loading of the “Bootstrap” scripts” at the client side of site at the General Booking Settings page. The Bootstrap files are required for the working of the plugin, and you can deactivate it only if the theme or some other plugins is already loaded it.
If you are activated those scripts, and have no visible calendar atthe site, so most common reason of not loading actual version of the jQuery. The booking Calendar version 4.0 is require at least version 1.7.1 or newer of the jQuery.
The WordPress installation 3.3.2 have this jQuery package inside of own installation, so if you are use the older wordpress installation, please update it.
Please check the troubleshooting instruction here: https://wpbookingcalendar.com/faq/calendar-not-visible/
More detail about this issue:
Error: a("body").on is not a function
Source: .../booking/interface/bs/js/bs.min.js
Line: 7
Solution:
Its seems, that this issue is because your theme is used the old version of jQuery.
Please, download the latest version of jQuery and integrate it into your actual theme or just use the latest version of jQuery from WordPress installation (just comment loading of the jQuery from the theme and the Booking calendar will add load of the jQuery from your wordpress installation (of course, recheck that this installation also have to be up to date))