Today my power fluctuated for about 3 seconds and when the ST Hub (V2) reconnect, it will no longer change status of my devices. It detects my lights are on but if I click to turn it off it turns gray and says “TURNINGOFF” but the action never completes. Even more, I can’t see the requests in live logging so i don’t think anything is actually happening when I press the button on the phone app.
I also cannot use Google Home to control the lights either.
Anyone else ever had this problem?
I’m sure that’s very frustrating. 
A power surge can fry any unprotected electronic device, including the hub. But first you can just try to resync it.
Take the batteries out of the hub if there are any and check them carefully for corrosion or damage.
Unplug the hub and leave the batteries out for 20 minutes.
Now plug the hub back in. This will force it to re-sync with your cloud account.
If that doesn’t solve the problem, you’ll need to get in touch with support.
Thanks! It was actually attached to a surge protector so maybe it just only needs the re-sync. I appreciate it!
I was notified of a power outage today by the power company and received a notification from the SmartThings app that the Hub was disconnected. The Hub had batteries maintained power.
When I got home my Google Home devices would not communicate with the Hub and the SmartThings app would not connect to the hub even though it said the Hub was online.
After rebooting my router, Philips Hue hub, and my SmartThings Hub it still had the same problem. It took several more reboots before I could get it to partially work. It had trouble communicating with the Philips Hue hub and would turn on and off devices several minutes later and not communicate with others at all but would change their status on the app.
I was able to get it running after an hour and a half.
They’re definitely needs to be something done when there’s power failure issues.