How can I sysc Google calendar with my Pixel 2XL and Oneplus 5T?

[Android Central Question]

I have the following devices...
Nexus 7/2013
Nexus 9
Pixel C
Samsung Chromebook Pro

With each of these devices my Google Calendar syncs with the main calendar on my PC.

I also have a Pixel 2 XL and a Oneplus 5T. On these devices, I am unable to sync with the other calendar (my wife's).

On the devices where sync is working, her email address shows up below Events and Reminders (click on the Hamburger or swipe left to open the "Google Calendar" page.)

On the other two devices, there is nothing below Events and Reminders.

I have restarted the devices many times, cleared the Calendar data and Cache but I have been unsuccessful. Any suggestion would be appreciated.

 

[Rukbat]

Go to the Google Calendar page for each account (on the phones) and add your wire's calendar. Then the phones will see it (in about an hour or two).

 

[delpi767]

That's the problem. I can find no way to do that.
Under accounts all I can do is toggle Calendar on or off.