Known issue that many have been facing for a long time now.
Try to disable IPv6:
If you can't edit settings due to the metwork being detected as offline, try to power cycle/ reboot the main/ master puck first.
I've seen this as well. It started with a recent update to the Google Home app. Can you try dragging the home screen in the Google Home app down until the refresh spinner starts spinning? That seems to correct it for me (at least until the next time I have to restart the Google Home app on my phone).
Hmm, that has never been a problem for me after I disabled IPv6 a long time ago. But maybe there can be multiple causes.
Least destructive: Try this suggestion first. 🙂