Passenger not detecting Rails app

I’ve just switched my entire site over to a Rails app, and am trying to run it with Passenger instead of FastCGI. So deployed it, used the web panel to point the domain at the app’s public directory, and switched on Passenger. But instead of the app, all I get is a plain Apache directory listing of the public directory. No errors in Apache’s or Rails’s logs. Anybody ever run into this?

I have a ticket with support, but the 24-hour turnaround on responses is driving me crazy.