I have two Nest Wifi routers set up in my home network, configured as detailed in the support pages. The setup is
(✓) Modem → Google Nest Wifi router → Switch → Google Nest Wifi router
Everything was working like a charm, until I recently started getting some very specific issues when connected to my wifi network. The two most noticable examples: controlling my robot vacuum and downloading/updating apps from the Android app store. I have the impression that the problem is in my Nest Wifi setup:
I am a novice when it comes to networking, so my apologies if I've mixed up some terms/concepts here. It seems like my robot vacuum is fine sending information to the cloud, but my wifi-connected devices are having trouble fetching that information. Same thing with app updates: our phones know that there are app updates available, just can't download them.
AFAIK, I haven't made any changes to my Nest Wifi settings. I have also factory reset both my vacuum and my Nest routers, but the problem persisted with default settings.
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.
Sounds like you are running double NAT, referring to you writing about your ISP firewall. This is not recommended, the primary Nest Wifi acts as a router with firewall, NAT and DHCP. So best practice is to put any equipment in front in bridge mode.
I'd also try to toggle IPv6 on or off in the Google Home app Wi-Fi settings, this seems to have been causing issues the last couple of months. There is a new firmware version rolling out these days that is said to fix IPv6 problems, but until then, try to toggle it on/ off (oposite of its' current setting).