Cannot get a song to match with identify GET

Observation #1 --

When I run:

http://developer.echonest.com/api/v4/song/identify?api_key=&version=4.11|4.12&code=, I get back an empty songs array!

When I run without any version parameter, I get the full identification response in JSON.

Observation #2 --

I built and ran the iOS code from rexstjohn/echoprint-ios-sample on iOS7. Here, when I pass the statically-defined PCM code to the same server, I find the same behavior as noted above - i.e., I must run without version number to succeed in identification.

However, most importantly, as many others have reported, I still cannot get any song to ID via the microphone capture. I have been trying many songs played through iTunes over the air, after verifying that the song was in your list of songs from the DB.

Help!