This error means license can't be verified due to:
-
internet connection abruptly stopped during activation or it's not possible to establish secure https session.
Please try to activate again -
you're behind some router which requires authorization and redirects to some login web page.
Please try to open any site in a mobile browser first -
Poweramp APK is not genuine (hacked, moded).
Please download and install Poweramp APK from https://powerampapp.com