To
sync your Gmail on iPhone and computer, first, use the USB cable to connect your iPhone to the computer that came with your iPhone. Now, select your iPhone in the iTunes source list and name your iPhone. Choose whether you want iTunes to automatically synchronize your iPhone's contacts, calendars, email accounts, and bookmarks. This is how to sync Gmail on iPhone. If still mail is not syncing, move to the 'Settings' then 'Passwords & Accounts' then tap on 'Fetch New Data.' Now, check if your Gmail account is set to Push, Fetch, or Manual. You can also change how often the device will fetch data.
