@MuhammadRizwan
If you want some suggestions from others in this forum, it would help if you provided some specifics, such as which Google Nest doorbell you have, how long you've had it, when you started having problems, and which notifications (doorbell press, "visitor announcements", event notifications) are not working.
Or you could try contacting Support to walk through the issue with them:
1. Go to https://support.google.com/googlenest/gethelp.
2. Select a category/product family, and type in a brief description of the issue, then click "Next".
3. Click "Other", then click "Next step".
4. Under "Resources", just click "Next step". (Clicking one of the listed links will bring up a Help page page.)
5. Under "Contact options", choose to get a phone call or chat with the team, depending on availability in your country.
