DIAGNOSIS This is an app connectivity bug, not a network outage. The app can't reach eero's cloud servers to fetch status, but your local internet is functioning.
FIX Force-quit the eero app on your phone and reopen it. If that fails, restart your phone's WiFi and/or cellular data. The app needs an internet connection on your phone to talk to the cloud.
IF THAT DIDN'T WORK Log out of the app and log back in. This refreshes your authentication token which can get stuck. You won't lose any settings.
HEADS UP If your network is truly working (devices have internet), ignore the app status. A full network restart (power cycling modem and all eeros) is only necessary if your devices also lose connectivity.