Satellite UHF Beacon Decoder

I am working on creating a cubesat satellite beacon decoder using the
Ettus B200 SDR.

I think I have a pretty good handle on the signal conditioning and the
demodulation (see picture of waveform and block diagram). However, for
some reason I am not able to decode anything. I think that I am going
about decoding the beacon (AFSK1200) the wrong way. Does anybody have
any pointers?

Thanks,

Patrick Barone