Is there somewhere you can go to use a laptop and desktop version, rather than the phone app? I keep reading on this forum about ´problems with the app. I guess you didn't by any chance make a note of the hosts' phone numbers? If so, you could phone or text them directly to explain the problem and get the codes, check-in info, etc.
As a host, I always write down upcoming guests' phone numbers and coded airbnb email address, hard copy, in case something screws up with the website.