Firstly try to find what plugin or may be theme is generate this issue.
- Try to deactivate one by one all actual plugins to check if the calendar will show up or not, to find what plugin is generate this issue.
- If the previous do not help, try to deactivate the actual theme and activate the default WordPress theme, then test it, if the reason of issue in the actual theme.
Some other possible issues.
Error: a("body").on is not a function Source: .../booking/interface/bs/js/bs.min.js Line: 7
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)).
Error: jQuery("#calendar_booking" + bk_type).datepick is not a function Source: .../wp-content/plugins/booking/js/wpdev.bk.js Line: 161
So then please check the troubleshooting instruction here.