https://www.xda-developers.com/how-to-fix-device-not-certified-by-google-error/
- Find your device’s GSF Device-ID. There’s a simple app on the Play Store called ‘Device ID‘, but since you obviously can’t access the Play Store I have mirrored the application here.
- Open the app and copy the code in the second line called “Google Service Framework (GSF).”
- Go to this webpage.
- Enter your GSF Device-ID in the “Android ID” box.
- After you tap “Register”, your registered ID should appear on the page.