*Go to SETTINGS -> GUEST MANAGEMENT -> AUTO ACTIONS
Consider the bookings that were cancelled and how to identify then so you can send the URL to those guests. Did you apply a Booking Info Code, or add NOTES?
Trigger tab :-
Booking Status = Cancelled
Booking Info Code = COVID19 (for example)
Message tab :-
Enter the text you need to send to the guest with the Special Booking Page.