I have also seen my problem described in several groups on Facebook, both of Shelly users and Smarthings users.
Without an apparent logic, suddenly all shellys in the Smartthings app are disconnected and no longer work. At the same time, everything works perfectly from the shelly app
To get them back active every time I pretend to add a new device by brand, I click on shelly and from there I am asked to redo the loghin. After the loghin, everything returns to normal functioning.
This is a FB group with the same problem:
Shelly’s CEO says they haven’t changed anything in over a month, but Smartthings changes something very often.
Does anyone know who we should contact to solve this unpleasant problem