Ok, now I see it.
Right now you are have this error at the page:
Error: jQuery("#calendar_booking" + myParam + tooltip_day_class_4_show).popover is not a function
This error can be a reason of that issue.
And its seems, that you are deactivate loading of Bootstrap library at the General Booking Settings page. Please reactivate it, for loading of those library.
If you have loading of the bootstrap, which is included into your theme or in some other plugin, so then this package of bootstrap have to include all "plugins" which is supported by bootstrap. Especially the popover plugin, which is required by Booking Calendar.