I am experiencing this too. Original hub, new app. The thing is, I use the app and control the device that says it is disconnected just fine! There is no reason it should say disconnected - it is a Z-Wave plug-in module that I use every night. It is on the quick-access of my phone so I would not have noticed it except that I slid down to access the light and hit it, but I saw that it said disconnected and it went to the full app dashboard instead, but I was able to operate it just fine. So now I cannot get it to stop showing disconnected meaning I have to go to the full dashboard every time to operate it, but it works fine. I tried the Edit/Update trick in both the developer web UI and in the Android App to no avail - it just wants to think that it is disconnected! Anybody else have any ideas? Hub shows disconnected too - if a power glitch caused this should I try a deep power cycle of the thing?
Mine fixed itself after about a month.
I figured out a fix. Pull the power on the hub and remove one of the batteries so that it is totally dead, give it a few seconds and then plug in the power and then the battery, and when the network realizes it is back up it will show everything as being connected again.
Thanks for passing on what worked for you. Sadly, it didn’t help me.
My v2 Hub in the new Smartthings IOS app still insists that about half my switches and sensors are disconnected. Meanwhile they show as connected in the Classic app, ActionTiles, the web interface, etc.
Amusingly(?) when I click on a “Disconnected” device in the new Smartthings app, it will actually correctly show the current status of the device before immediately going back to the previous screen because that is of course nonsense what with the device being “disconnected” and all.
I thought I would post what finally ended up working for me.
I was in the same position of items showing disconnected on the app but showing they were online in the IDE. I could even control them from the app when it said it was disconnected.
I ended up deleting each item one at a time from the IDE and then adding it with the app on my phone. They are now all showing connected and working. This was a lot of work and I know I read where people said there was no way they would do all that work. But this is what worked for me. Before I did this I tried everything else discussed in this thread and nothing helped.
Good luck. I know it’s not the optimal answer and we shouldn’t have to do this but it is a way to get it working. I would suggesting trying one item first to see if you have the same results as I did.
Anybody get this to work yet where it shows all your stuff connected? I would like to use the new app but I guess I will be using the classic app for now.
I have the v3 hub. I was having the issue of most things saying disconnected even though I could still control them with the new app. I unplugged the power cable and left it unplugged for about 5 min. Once plugged back in and it rebooted, everything showed up again just fine.
Everything was working fine until today, 03/30/2019. In the new app, Android, all of my GE Z-wave devices show disconnected. The show up and work on the web site and in the original app. In the new app if you click on the disconnected items arrow you can see the actual status and turn the device on and off. The only problem is in the new app. My hub is version 3 US. Since this is a very specific error in the new app I think I will wait a day or two before deleting and adding back.
try a reboot first. don’t delete anything.
Thanks, that worked
Tim
You may want to edit your post and remove all your personal info 
Most likely you replied by email which attached your signature file
I say we all pitch in a little to purchase Iris and bring it back online. Never a problem with Iris. And I didn’t need to drag a batteryless hub around with an extension cord to set up devices. Ive tried everything and all my devices still show disconnected.
OK, add my name to the list of people with disconnected devices that still function in the new SmartThings app.The interesting thing is that it seems to be completely randon. I have 3 devices that are showing disconnected. The first is a Leviton Zwave switch ( DZ15S-1BZ), in the same electrical box as this switch is another switch of the same model that shows connected. The second device is a Leviton Plug-In Lamp Dimmer module ( DZPA1-2BW). There is another Lamp Dimmer Module (same model) that shows connected that is about 6 ft further away from the hub than this one. Finally I have a magnetic door sensor from Neo that was just installed yesterday that is showing disconnected. All three of these devices function correctly with alexa and show as connected on Groovy IDE. Based on the posts, I guess I’m headed down to unplug and remove the battery from the hub. Seems like it is always something.
or try a reboot from the web IDE
That would have been a great idea prjct92eh2 but I didn’t see it until I came back up after going through the reboot. It did fix my issue, but that is pretty annoying.
The new app has issues whenever the hub disconnects and reconnects. Sometimes it thinks hub connected devices are offline when the IDE and Classic app think otherwise. A reboot from the IDE always fixes it for me.
Hey guys. I may have a possible fix. I had the same issue as most on here. After the latest update, most of my devices showed as disconnected. I have a V2 hub. I tried disconnecting the power for a few and then rebooting but it did not help. I then disconnected the power again AND the network cable, waited about 10 seconds, plugged everything back in and voila, everything showed connected again. Hope this helps someone.