The SB8200 has 2x ethernet ports. Most users believe that both can be used but sadly, most ISP’s only support 1 connected device. 

So make sure you only have 1 device connected to the SB8200. 

Power the modem and the router off and disconnect everything (even coax) from them. 

Leave them off for around 5 minutes. 

Then connect coax back to the modem and power it on. 

Wait 2 minutes. 

Connect lan port 1 on the modem to the google router and power it on. 

give it a couple minutes to boot and try to go through setup on it.