Hub Offline but

iPhone reports hub offline every few days. App also displays “Hub Offline” in red at the top. Yet, I am still able to control my things with wifi turned off on the phone. This means the hub is connected to the internet, but the “Hub Offline” continues to show up at the top of the screen - sometimes for hours before it goes away. Closing the app doesn’t change anything. Anyone else experiencing this?

My best guess would be your router is blocking some type of traffic.

Here is what I would do.

Unplug your internet modem.
Unplug your router.
Unplug your SmartThings hub.
Reboot your phone.

Once your phone is back up, plug in your modem.
Once your modem is online, plug in your router.
Once your router is online, plug in your SmartThings hub.

If your problem continues check your routers firewall and/or setup a static ip for your hub and add rules for ports 37, 39500, 1111, 9443 to route to your ST hub. The static ip and port forwarding should not be needed but worth a try.

I have noticed this with iOS as well. In all cases, my hub is definitely online since the app is functioning to control my devices. I have just started to ignore the warning.

Never seen this with Android. My guess is an app issue, we have our fair share in the Android app, just not this one.