@Sylenka0
Did you manage to find any resolution in the end?
That's a very tricky situation. I don't know what else you could have done except cancelled the upcoming booking. Of course, there are a lot of penalties for hosts who cancel, but you had little choice.
The extenuating circumstances policy only covers COVID related cancellations if either the guest or host contracts the virus. However, you are right it doesn't make sense that the host gets penalised for having to cancel a booking because someone else at the listing has tested positive. Even if your Airbnb guest had checked out in time, you couldn't expect the new guest to share with your tenant in that situation.
I am not sure what you mean by your offers have disappeared from your listings. I have heard here on the CC that some listings are being temporarily suspended (and upcoming bookings cancelled) when Airbnb is informed that someone who stayed there has tested positive, but I am not sure if that is true or not. I haven't seen anything official about it.
Probably why you are not getting any answers from Airbnb CS is because they don't even know themselves.