Hello,
It is clear to me you allready have the Airbnb phone-number and other contact possibilities.
Also twitter @AirbnbHelp sometimes works fine for a quick answer.
Looking at your case, from my personal(!) opinion as an airbnb- host, you made a mistake:
You made a reservation, but afterwards wanted to cancel it.
You had to contact Airbnb immediately to explain the special situation and ask them to cancel.
Or you had to cancel it yourself and then contact Airbnb (within 24 hours) for a refund of your cancelation-costs, referring to the "special circumstances".
Asking the host to cancel is not correct, it's not his fault or problem you don't want to stay there anymore.
If the host would have cancelled your reservation, he would also have been penalised by Airbnb, that's not what he wants.
If Airbnb is not responding, your only option left is asking the host to pay you back some of the money via Airbnb resolution centre, as a gesture of goodwill.
Please read also:
https://www.airbnb.nl/help/article/544/what-is-airbnb-s-guest-refund-policy
Best regards,
Emiel