A message was refused
A message in a conversation is refused when it contains a phone number, an email address or an external link. It is not sent and does not reach the other side.
The check is on the text itself. Digits spread out with spaces or written as words are read as a number, so an indirect phrasing is refused too.
To carry on, write the message without that detail. Whatever needs arranging can be arranged here, inside the conversation.
The moment a booking closes on the listing, the check stops applying to that conversation, and the phone number and the address open in it anyway.