Poweramp Play purchase (Poweramp Full Version Unlocker) is per Google account. This means app can be used on multiple devices as long as devices have your Google account.
Please ensure proper Google account is registered on your phone and selected in Play app. Then install Poweramp Full Version Unlocker from Play
If it shows it as paid app with the price: app double purchase to the same account is not possible on Play, it will refund/cancel your 2nd order immediately and Play will d