page not working

Hi I have installed this on http://www.caravanhirewales.co.uk and the booking system works great with the site sidebar.

However it does not work with the date checker page http://www.caravanhirewales.co.uk/check-dates/

Just updated to 4.3 to see if that would fix the issue, it did not – where am I going wrong – please can you give some guidance

https://ww.wp.xz.cn/plugins/booking-system/