Play Store not opening? Device not certified? This guide fixes 90% of Google Apps issues after a custom ROM flash.
When you flash a custom ROM, Google's servers see a new device fingerprint. If the ROM's fingerprint isn't certified by Google (which many custom ROMs aren't), the Play Store shows errors like "Device not certified", apps fail to install, or Play Protect behaves erratically.
The good news: this is almost always fixable in under 5 minutes.
This fixes the "Device not certified by Google" error:
Banking apps use Google Play Integrity (formerly SafetyNet) to detect rooted or modified devices. Fix options: