Please follow the below steps:
1. Check vibration settings:
Go to Settings>Sound & Vibration>Vibration and toggle on Vibrate for Calls and Notification Vibration/Touch Feedback.
2. Press the volume key to enter the ringtone Volume Settings. Click the ringtone icon and check whether the vibration switch is turned on.
3. Reboot the phone and test again.
4. Back up all data and restore the phone to factory settings.
If the issue persists, contact the Nothing Support Team for further assistance.