Hello @Anu2013 ,

Try this, I'm not sure if it is works or not,..

1. Impersonate user (user who not receiving notifications)

2. Go to Preferences

3. Select Notifications

4. Check Allow Notifications enabled or not. Click on Advanced Preferences (it opens in new tab) 

5. Search table from Search Notifications (for which table user not receiving emails)

6. You can find notifications below, check if any notifications are in off mode, then enable