I'm trying to send someone a special offer (because they sent a message saying they were a couple but the accompanying reservation request is for one) but the system is telling me I've marked some of the dates in question as unavailable. It's for one night - tonight - and someone checked out this morning but tonight is available. Tomorrow was blocked out but I made it available in case that was the problem but it doesn't seem to have made any difference. I haven't accepted or declined their booking request. What could be causing this and how do I fix it?