Even though this is an old thread, this stupid problem remains. I tried reporting it through the android app at least a year ago with no response. Now I will post on this forum, and also expect no help.
I have a Samsung Galaxy S7 Edge. All of my music is stored on a micro SDXC card. I purchased Poweramp a long time ago. EVERY TIME I try to use Poweramp while flying it will work for perhaps half an album. Then it stops and I get the unable to verify purchase through Google Play message. At this point I can no longer use Poweramp until I have landed and get to a place with a strong wifi signal. This "bug" is real. It should be fixed. I like Poweramp, but my most important use for the program is when I don't have an internet connection. Please somebody with Poweramp, fix this long standing issue!