In my experience, when I use the verbal command "Open Izzy", then follow with "Turn on dining room" or "Turn off dining room", then the device works as expected. Only issue with this approach is having to go through the full UDI Alexa spiel each time.
However, when I issue verbal command "Tell Izzy to turn on dining room", then I get the response, that the device is not in my profile. I currently only have the master account in ISY portal, investigating if I need to setup a separate user account.