I was reading through project Fi help info and under protection plan has some good info for people who ordered there phones through Fi who didn't get the protection plan.
It says
Add Project Fi device protection
To enroll in Project Fi device protection, you must purchase your phone through Project Fi. You can add device protection when you purchase a phone or within 30 days of the phone’s shipment:
So you should be able to add it in within the first 30 days.
Hope this was helpful
Link to page
https://support.google.com/fi/answer/6309809?hl=en
It says
Add Project Fi device protection
To enroll in Project Fi device protection, you must purchase your phone through Project Fi. You can add device protection when you purchase a phone or within 30 days of the phone’s shipment:
So you should be able to add it in within the first 30 days.
Hope this was helpful
Link to page
https://support.google.com/fi/answer/6309809?hl=en
