Oh yes...the FCDPP is the "standard" SDR that FoxTelem folks use. Tell us more---you have a "strong signal". Does that mean you have a nice "hump" on the FFT (bottom) line? Are the "demodulation bars" surrounding it? Do you have an eye pattern in the right box? Two thoughts: 1) It is not as strong as you think and you need to check LNA or IF Amplification. 2) Although you can see the signal with you own eyes, FoxTelem is not looking at the right frequency. Be sure that under "spacecraft" and either AO-85 or AO-91 the nominal, min, and max frequencies are ok. Nominal should be 145980 for AO85, 145960 for AO-91. Min and max should be 10Khz below and above that.
Oh, and what version of FoxTelem do you have? Older versions might not recognize AO-91.
Good luck and 73,
Burns, WB1FJ