How to Fix Gmail Not Syncing on Android

– Perform a manual sync. Open the Gmail app and swipe from the top of the screen to the bottom. You should see a refresh icon, at least briefly, as the app syncs with Gmail’s servers.

– See if Gmail is down. Google provides a way to see if there are any known issues with their email service. If there are, there’s nothing you can do but wait.

– Verify that you’re online. You must have an active data connection, whether it’s Wi-Fi or mobile data, for Gmail to pull messages from the server.

– Clear the Gmail app cache. This is often a fix for a corrupted cache, which could be contributing to the syncing problems.

– Restart your device. Sometimes, a quick reboot is all that’s necessary to get a smartphone or tablet to work again.

– Update the app. Downloading the latest version of Gmail may fix problems with syncing if the issue stems from a software bug.

Credit : https://www.lifewire.com/what-to-do-gmail-not-syncing-4177194