Hi,
We are sorry to hear that. The version 1.7.3 introduced a new dates-range picker calendar, but it’s still based on the WordPress native jQuery UI Datepicker calendar that ships with every WordPress installation. This means that the new dates-range picker calendar of VikBooking should work exactly like the single-date picker calendar of the previous versions.
It may be possible that third-party plugins are minifying or caching some JS assets, and so flushing these settings should fix the issue.
We tried to visit your website page, but unfortunately the bookings are disabled in VikBooking, and so the JavaScript error is not visible. We kindly ask you to open a ticket from our website or to use the contact form so that we can provide better assistance to your case, if flushing the cache from any other third-party plugin will not solve the issue.
Thank you,
The VikWP Team