@Sam397 , I have tons of experience giving virtual vouchers to guests who have had to cancel. In my case, over the years, it has mostly been because of floods. My treehouse is on a floodplain, and if a guest isn't a canoeist who wants to come anyway, I don't make them pay, even if they cancel same-day. The river rises and falls quickly. It's part of my deal here. No one's fault. I don't expect to make money on it.
I have to do it with trust. I tell them the next time they book to send an inquiry and I will send a special offer. They have my word on that in the messaging. I tell them to point to that as proof.
Because, yes, there is no way to issue an actual voucher that I have found. I wish there were!