Customer left in a lurch when rental site switched

QI booked an apartment in Paris on Airbnb recently. At the last moment, the host gave me a different address and said, “It’s the same street.” But it wasn’t the same apartment. I decided I didn’t have much choice, even though it was suspicious. When I arrived after a trans-Atlantic trip, I knew I couldn’t get into the apartment until 2 p.m. But I had heavy luggage, so I went to see if I could drop it off if the current tenants were still there. The owner was at work and couldn’t be contacted. I had instructions to pick up the key at a nearby building, which I did. The key did not fit the apartment door or, indeed, any doors around. Tired and at a loss, with no backup plan provided by the host, I sent her a cancellation and got a hotel nearby. I offered to pay the first night’s rent, but neither the host nor Airbnb would refund the remainder. Now Airbnb is ignoring me, as is the host. I can’t even leave a warning review since the reservation has been removed. I am out $500 plus the considerably more I had to pay for a hotel. What can I do?