You don't initiate contact with support from your Inbox. You have to go to the Help pages, follow the prompts and drop down boxes until you get to "Contact us" (you can also contact them through their Twitter account) and write your message there. When you get an answer in your Inbox from them, you then continue to communicate with them by typing a message in the box provided under their message to you and hitting Reply.
As I tried to explain above, if you arrive to an Airbnb to find it unacceptable, the protocol is to first contact the host to tell them what's wrong and give them an opportunity to correct it. You don't message the host asking them for a refund right off the bat. There are issues that a host can and may correct- perhaps their cleaner did a poor job or unbekowst to them, never showed up, something like smoke smell can't be corrected in the moment, but some hosts have several listings and might apologize, and offer to move you to another unit, or pay for you to stay the night in a hotel while they deal with the issue. You have to at least give the host a chance.
Now if the host is unresponsive, rude, says they can't do anything about it, then the next step is that you cancel the reservation, or contact Airbnb to do it, letting them know why you are leaving and they will likely just issue you a refund right then (which may take 2 weeks to show up in your account). If you can't get ahold of Airbnb at the time, then you have to talk to them about the refund as soon as you have a chance.
What most guests don't realize is that hosts don't get paid for bookings until 24 hours after guests check in. From the time you pay for a booking, until then, Airbnb has your money, not the host. All money transactions, whether they are the booking fee, or a refund, go through Airbnb.
Hosts can choose to refund guests by using the Resolution Center to send money, but honestly, a host who would let guests check into the sort of disgusting scenario you arrived to find are not the type of people who you should bother asking for a refund,. because they aren't the type to give one. Let Airbnb deal with refunding you.
BTW, all this info about what to do, and the order to do it in if you arrive to find a bad place, is info that is readily available to guests in the Help articles for guests on the main Airbnb site (not this forum), if only guests would bother to read that info.
Sorry you had such a bad experience, and hope it gets resolved soon. Hosts who would offer a filthy place should be banned from the platform.
@Jay1463
@Jay1463