Hello there,
I’m experiencing some issues after the last update, the SmartThings App in Android (not classic, v 1.7.45-28) is currently showing my Hub as Offline, but I can tap into it through the app, see details, ping it using SmartThings IDE and talk to the connected devices.
The hub is an ADT Hub and can also interact with it Arm/Arm Away/Disarm using the app despite showing as offline in it.
Any advice? I remote rebooted it using the SmartThings IDE
Try signing out of the app and signing back in. If that does not resolve the issue, contact ST support and let them investigate it for you. 
Didn’t work, I uninstalled it, installed it again, logged in and still show as offline.
I did a different test tho, I actually disconnected the hub from Internet, now the ADT Widget shows that the hub is offline, then I connected the hub again and the message inside the Widget shows that the hub is online, but the App still shows as Offline at the top… weird!
ST support can investigate the issue for you. If you are in a region where you can call them, that is usually the best method to contact them for a faster response.
Thanks for the advice @jkp but it will not work for me as I’m using ADT Hub outside of USA, I’ll keep trying other things