Here is a compiled list of things to try when your phone is not vibrating for notifications:

1. Check if silent mode is activated
2. Check if Do Not Disturb mode is activated
3. Check if Vibrate is enabled in sound settings
4. Check if notifications are set to ‘on’
5. Remove the battery, wait for 5 minutes, and reinsert the battery
6. Restart the device
7. Consider restarting the phone in safe mode