Join Date: Feb 1999
Location: San Jose, California, USA
Programs: AS 100K, UA MM, AA MM, IC Plat Amb, Marriott Gold, Hilton Gold, Hyatt Explorist
Posts: 3,146
I have not run into this situation personally, but perhaps you'll get a response from someone with first-hand experience.
Alternatively, I would directly contact the hotel to see whether they will honor the reservation as booked. Of course, you won't get any Accor benefits (if these apply to third-party bookings), but at least you'll have a room. However, with third-party bookings, the travel agent that accepts the booking doesn't always transmit the reservation information to the hotel until just before the stay.
Therefore, I would next check with whoever charged your credit card for the booking. I'm guessing that is booking.com; if so, then they are your agent and should either reconfirm the booking with the new hotel or return your money. You might also ask them to find a suitable replacement for the money you've already paid.
Lastly, due to the third-party booking, I think that Accor would be the least likely to be able to help, but hopefully one of the above approaches will make things right.