If your Gmail account is not synchronizing on the Mobile device then, all you have to do is to-
- Close the Gmail app if it is running
- Now, on the Mobile devices and then, open the Settings
- Touch on More in the top-right corner
- Check on the Auto-sync data to enable the synchronization
You are all set with the synchronization issue and if still Gmail is not syncing then, all you have to do is to take instant help from Gmail Help care Number UK from the experts regarding the same.