Hello there!
Sorry for the delay.
Please be informed that our Hotel Booking plugin has nothing to do with the issue that you currently have. Take a look at how your booking confirmation page is built and what happens with the “Accommodation Types” widget or the sidebar when you select the number of guests on mobile devices. Well, even without it, the “Accommodation Types” widget overlaps the “Book Now” button and this is exactly why it’s not visible on mobile devices. But, for a yet unknown reason, when you select the number of guests, the sidebar extends its height, slides up, and covers the form too.
I tried to play with “z-index” and sidebar positions, but I still can’t seem to understand why it extends its height so much when you select the number of guests. Most likely that the reason is in the theme that you use or in the way you built the page.