Can’t add ics calendar invites from outlook to Google calendar on iPhone

Hi emerybord9, We appreciate you reaching out to us. We’d like to gather additional details that may help us be in a better position to assist you.

Does it seem like the issue is isolated to invites sent by certain contacts?

If no, let’s make sure that you are running the latest version of iOS 16.

While it isn't inherently assured that an update will resolve the issue, updating to the latest software version for your device can help isolate potential software issues. 

Kindly secure a backup and update.

1. How to back up your iPhone, iPad, and iPod touch
2. Update your iPhone, iPad, or iPod touch

Then, make sure that both your Outlook and Google Calendar are up to date.

1. "Open the App Store.
2. Tap your profile icon at the top of the screen.
3. Scroll to see pending updates and release notes. Tap Update next to an app to update only that app, or tap Update All."

You can use the article below as a reference.

How to manually update apps on your Apple device

Please keep us posted.

Take care!