You are not getting emails on the Gmail app, and also having calendar sync issues on the mobile app.
You must enable IMAP.
- Go to mail.google.com on a computer.
- Click on the settings icon in the top-right corner.
- Click See all settings.
- Click Forwarding and POP/IMAP.
- Under IMAP access, select the option Enable IMAP.
- Click Save changes at the bottom.
- Then, open the Gmail app again.
After performing these steps, you will start getting the emails on the Gmail app, and the events on Google Calendar will start syncing.
If you have already tried to remove and then add the account from the Gmail app, and you have also tried to uninstall and then reinstall the app, and you are still not getting the emails, or if you are having sync issues with the Google Calendar app, turn on IMAP on the Gmail settings.