Is it possible that the plug-in does not support the gen 2 devices?
I have been unable to connect Shelly1 Plus, Shelly PM Plus and Shelly 2 Plus with Indigo.
For the MQTT topic root, I have used: shellies/shelly1-B8..., shellies/shelly1pm-B8..., and shellies/shellyswitch2-C0... respectively. For the shelly2, I have also tried ...switch25 and ...switch2.5.