Hi Smartthings community,
I have Smartthings Wifi model ET-WV525 (3 hubs) . One of the hub died (the main one) and won’t power on anymore. After a power reset on the remaining 2 hubs I’ve changed the main hub. But now Smarththing still shows has offline … When I click Use SmartThings Hub, and then make sure the switch is turned on, I get the message “A network or server error occurred. Try again later”. Please don’t tell me I need to re-register all my devices !!
I think I found the answer Smartthings wifi et-wv525 dead main unit … But I wont do the same mistake (sort of), time to ditch Smarthings for Homey with the hope that LG won’t pull a Samsung.
Did you try replacing/substituting the power supply for the unit that fails to power up? It may be as simple as that. 
They very well might: it really is all about the money and to where the appropriate marketing department believes the future exists!