Hello, you are right. It doesn't work. It will be fixed in the next version.
If you want to fix it immediatelly then open file administrator/components/com_booking/helpers/booking.php and search rows look like:


after this rows put:

Thanks, it woks.

Here I got the same issue. Thanks for posting the code, it worked.

Nevertheless: I bought a system which I expected to work free of errors. Other companies in the software industrie have a point: "known issues" I you know already the solution for certain errors, you should publish them to keep customers away from going crazy be searching for the error.