You can still find the previous messages under Menu, Reservations, but they're no longer an ongoing thread when a guest books again. It's now up to the host to remember or check that it's a returning guest ...
I'm sorry you are dealing with this issue at the moment. Shelley shared with you great advice on how to fix this. Thanks @Shelley159! Were you able to check this?
Since Monday, were you able to get this messages back? If not, I'm going ti attach this feedback form in order to explain the issue. This is the link. 👈