Just found out - after several resets - that an issue occurs when the IP of a Shelly device changed (before(!) adding it to Homey). For example if you set a fixed IP in your router/DHCP. The dialog page in Homey just stays blank after selecting the device, without any error message.
Restarting the Homey app fixes the issue (workaround), so it’s not that urgent but maybe there is a clean solution in the future. 
