Hello.
You have inserted shortcode only for the “availability calendar” (without form, where is not possible to select days, its only for showing availability). Instead of that you need to insert the shortcode for booking form with calendar.
Please open this page for editing, then remove exist shortcode.
After this switch from the “Visual” view mode to “Text” view mode your content editor. And then reinsert the Booking Calendar shortcode and test it.
Please note, this shortcode [bookingcalendar type=1 nummonths=1] is only for showing availability calendar, without form, where you can not select the dates.
In case if you need to submit new booking you need to insert the shortcode for booking form.
Please read more how easily insert booking form or availability calendar into a pages https://wpbookingcalendar.com/help/inserting-booking-form/ or how manually configure Booking Calendar shortcodes in content of your pages: https://wpbookingcalendar.com/help/booking-calendar-shortcodes/
Kind Regards.
