1 thing I see all the time is that people see the 2x ethernet ports on the back of the SB8200 and think they can use both. Sadly, most ISP’s only support 1 public IP address. Meaning only 1 device can be connected to it. 

If you had something connected to it, disconnect it from the modem, power the modem off for 10 minute, then connect the google to it on port 1 and power the modem back on. Once its on and booted, boot up the google nest and run its internet setup . 

Don’t plug anything else into the sb8200

The reply from plemans is correct.  I spent a couple hours on the phone with Google support to troubleshoot why I wasn’t getting internet access to validate if it was ISP, old modem, or router.  They instructed the same thing to only have the router connected to modem during setup, but said after WiFi is setup I could use the second port.  Obviously they don’t know what all the ISPs allow so I will be calling my ISP again based on the first statement they made.

Just got off the phone with my ISP, Cox, who told me the second port is only used for Fiber which I don’t have on my plan