Hi @Sue383
For the July dates:
Did you receive an email asking you to accept or decline a cancellation for this guest. If you clicked accept then "you" have cancelled and the dates are blocked by airbnb as punishment for cancelling a reservation.
August dates are still showing available, check your reservations to see if they rebooked.
What you should have done is go to the original reservation, click change and move it to the new dates.
If you still need it clarifying ring your dedicated superhost phone number for a quick response.