@Claudia-and-Mark0 A guest who doesn't have the manners to send the host a message when they cancel isn't worth wasting any more time on, IMO.
If I have a guest who sends a nice message saying they just came down with a terrible flu and sorry they had to cancel, I'd respond, saying I hope they recover soon and hopefully book with me in the future, but it would seem to be pointless to message a guest who just cancels with no communication. It's not like I'd even want them to book again.