Upgrading to premium will prevent ads from being displaying in the app and will also prevent the Upgrade to Premium screen from being displayed and stopping music playback.
Please note that internet radio stations you choose to listen to may still contain ads
The upgrade screen can be accessed from Settings (you may need to scroll down to see it)
Occasionally you might find that the app forgets that you've upgraded to premium., especially after an upgrade.
If that happens, here's a few things you can try to fix the problem:
Open the Play Store app and check that the selected account is the same as the one used to purchase the premium upgrade. You can verify that you have the correct account selected by viewing the purchase history in the Play Store app. Your Hi-Fi Cast premium purchase should appear there.
Restart your phone (make sure you're connected to the internet so that the app can connect to Google Play to verify the subscription)
Re-install the app (when installing, check that the account selected in the Play Store app is the one used to purchase the subscription)
Clear the app data in Android Settings
If none of the above helps, there might be a problem with the Google Play app or Google Play services on your phone. More information is here: https://support.google.com/googleplay/answer/9037938?hl=en
If you have recently upgraded to premium, check in Google Play that the purchase completed successfully:
Tap ☰ and then Account
Tap Order History and you should see your order
If everything looks OK, then try restarting your phone (make sure you're connected to the internet so that the app can connect to Google Play to verify the subscription)