@Rob8254
When it was about an inquiry the calender will not be blocked.it is not even mandatory to decline, just answer the question.
But when it is a booking requests , dates can be blocked under cirtain circumstances. (fe: you decline because of "dates not available"). But then you can make the dates manually available again.
How-do-i-make-dates-available-or-blocked-on-my-calendar
BTW when you cancel a reservation, dates will be blocked and remain blocked.