I purchased the code 50 amp in February and installed the Gateway app on my iPhone iOS 10 and the playback feature worked great. I currently have a Gateway app software 1.4.1 . Several months ago I realized that the playback feature did not work.  I wasn't sure at first if it was an update on the iPhone software but I figured it was probably a common problem and would be fixed shortly but it has been several months now and still having the same problem.   I also  tried the app on a different iPhone that had a different software version and had the same result. It looks like a similar problem was happening on the Google play app version and was fixed with the 1.4.2 software.  The playback feature can be selected and you can pick a song out of my library but it will not play.