Are you in the air when testing? You generally will not pick up IN traffic until 1000-1500 feet, depending on your position relative to a ground station.
The ADSB-470 it receives on 978, which is mostly from ground stations (not many 978 out AC to date). The Stratus receives on 1090 and 978, which will pick up the signal sent from other aircraft that send out on 1090 (most common).
If you have the Dynon 472 box, it is dual band but they are working through some issues with the software and hardware.