Many of customers are facing this issue , that they are not receiving cancellation URL in their mail
It is due to the payment method option you select and that is where many are facing issue
so first if you try to select ( test payment ) option in booking form then the client will receive mail template where cancellation URL will not be there.
So as you can see if you will not have any payment method selected then you will not be able to receive cancellation URL in your mail from booking appointment .