No internet when connecting through hub or router

@flatlander3​ Thanks for the response on this. I'll try to answer as best as I can, as a lot of this is out of my area of expertise.

My version of the MB8600 only has one LAN port.  Because there was only one LAN port on the back, I believe that the MB8600 was set to bridge mode with no way to change it.  The admin console for the MB8600 had very little other than the ability to review logs.

Originally, it was a direct connection from the MB8600 to my Google Nest WiFi router, and all my devices were connected to (and I assume) getting an address from that.  But as of yesterday, the Google Nest WiFi router reported no internet / network connection error (the error reporting or diagnostic abilities of this router are limited).  After rebooting the modem several times, rebooting the router several times, in different order and with the devices connected and disconnected, I finally factory reset the WiFi router to try and setup my home network from scratch.

So unfortunately now when trying to setup the Nest WiFi Router, it is not able to connect to the internet.  The MB8600 is rebooted, I connect the Nest WiFi router which begins its setup process, but fails when trying to connect to the internet (again, with no helpful errors other than the process failed).
When connecting a hub directly to the MB8600, all devices downstream from the hub also fail to connect.  A Windows laptop detects that it is connected via ethernet, but no internet, and doesn't appear to have any IP address assigned (although, not sure if that is because one can't be assigned, or some other reason)
When connecting a laptop directly to the LAN port on the back of the modem, I am able to successfully connect to the internet but only after rebooting the MB8600.  If I unplug the laptop and connect a different laptop, the MB8600 will need to be rebooted again to be able to connect successfully.

Sorry if this was a mess of a data dump, I am a bit out of my league when it comes to the specifics of this technology.  But because of the behavior I'm seeing, I am leaning towards it being an issue with my MB8600 and have no problem if it needs to be replaced, but would hate to get something new and still have all these issues.

Thanks again for the feedback

@flatlander3​ wrote;

MB8600 in bridge mode? 

FWIW. That's all that it can do. It's a straight cable modem.

@nardobolo​ Yeah, that sounds about right for a straight cable modem.  I was confused about the number of ports, and if there was a version with other options/different firmware than what they actually documented. 

When you hook up to the modem with anything, reboot/power cycle the modem to get connected.  At least that's how most of them work.  If you switch devices,  you will have to reboot the modem again. 

I think you are running into more of a google nest issue than an Xfinity issue if a laptop/PC works with the modem.  Are you using their phone Google Home app to try to set it up and does it have a QR code on the bottom of the router unit?  The instructions may vary a bit depending on the exact model number, but does this look reasonable for your setup?  The particular model is a GA01426 You may also have to delete a previous configuration in the phone app before trying to add this device back. https://manuals.plus/google/ga01426-us-nest-wi-fi-router-manual#axzz7o8Tw0eTN

 I'll add:  Connect Nest to Modem.  Power up nest.  Wait a couple of minutes.  Note the blink pattern as listed in the instructions.  Reboot the modem.  Wait some more time -- 5-10 minutes perhaps for it to train and sync up.  THEN try the phone app to add it.

Perhaps it's just a timing thing.