Please try the following:
1. Restart the game and see if this solves the issue.
2. Switch to the WiFi or data network and confirm that mobile data is switched on, and try again.
3. Go to Settings> Apps> See all Apps, and find the game app. Go to Storage & Cache to clear the cache and then restart the game.
4. Uninstall and reinstall the game.
If the issue persists, contact the Nothing Support Team for further assistance.