Google Calendar Not Syncing with iPhone ?
Use iTunes to Sync iPhone Calendar
If your iPhone calendar won’t sync with your outlook account then you may use iCloud to do this manually.
Your iPhone uses iCloud to store its data so this wouldn’t be a problem.
Google Calendar Not syncing With Iphone
Step 1: You will need to connect your iPhone to your PC using your Lightning Cable.
Step 2: first Open iTunes and choose your iPhone device.
Step 3: Now tap on Info > Sync Calendars with Outlook > and select All Calenders.
Step 4: Now tap on Apply to confirm all of these options which will sync your iPhone calendar with iTunes.
Check Outlook Calendar Default Settings
Your Outlook calendar account will have to be the default calendar on your device.
To check this, you will need to head over to settings > Scroll down and tap on Calendar > Sync > Now click on Default Calendar > and tap on Outlook Calendar.
In Case , if unable to Fix Google Calendar Not Syncing With iphone