Hi @Linda322,
Welcome to the Community Center! When, as a host, you cancel a booking, one penalty is that the dates of that reservation are blocked so that you cannot take another booking at that time. This Help Guide explains the penalties hosts receive if they cancel.
In order to avoid the penalties in this case (and worth bearing in mind for the future), you could have just changed the reservation.
I suggest you get in contact with Airbnb and they may be able to reverse the cancellation and allow you to change the booking instead.
I have moved your post here to a new thread so that it doesn't get lost in another discussion and is easier to find. I have also given it a title, please let me know if you want to change it!
Kirstie