Hi! The answer is arrived very quickly! "ERROR_CONTACTING_SERVER error is reported by Google Play Store app back to Poweramp when Unlocker from Play is installed; it's reported in the following cases: - Play Store app not loaded. Please start Play Store app and wait until it fully loads start page. Play Store app can fail to load, for example, during its self-updating. Please wait until it fully loads, them start Poweramp again - internet connection is not available/unstable or Play Store app/services are blocked from internet - (Android 2.x) Background data is disabled To resolve this issue: 1. uninstall Poweramp Full Version Unlocker 2. ensure you have internet connection on the device up and stable 3. install Poweramp Full Version Unlocker from Google Play Store app. Reinstalls to the same account are free. Installing Unlocker from APK won't resolve the issue 4. You may need start/wait a bit/exit Poweramp 2 times to reload license state." Starting the app two times after reinstalling the key from Google Play solved the problem, now my licence is checked.