Nest Router is behind a CGNAT, probably. Even if so, I would expect to see an IP address (private one beginning with 100.x.x.x) when I check it. Is the WAN IP only displayed when it's assigned a public IP address or anyt other case? This prevents me from checking if my router is behind CGNAT or not.
Alternative is to go to following web page while connected to the Nest Wifi router:
Or insert the ethernet cable going in to the Nest Wifi router straight into your computer instead? Then check the IP you get.
I just wanted to jump in real fast to see if you saw olavrb's reply and to see if you still needed some help on this or if you were able to get it sorted out. If you are still needing some help, just let us know and we'll be happy to continue helping.
Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.
It looks like we've slowed down here again. We'll be closing up the thread unless anyone else has any input or needs anything else. If so, just let me know and we can keep this open a bit longer.