Here are the solutions you can try to fix your Gmail not syncing issue:
If you are using Gmail on your Windows device, then first update the Windows Mail app.
Try changing the Email sync frequency on your Mail app.
It might be that your system’s firewall or Antivirus is interrupting Gmail. Try resetting the firewall and network protection settings to fix this.
Allow access to Calendar to your Mail app.
We hope after following the above solutions, you are no more facing issues with synchronization on your Gmail. If the issue persists, you must contact Gmail experts to get help right away.