I have Ikea Tradfri smart lights linked to my Echo via a Tradfri Gateway.
This works beautifully for me, but my flatmate (whose Amazon account is part of my household) is unable to control the lights. As I understand it, the expectation is that my flatmate should add these devices to his Amazon account in order to be able to control them. Unfortunately, the Ikea Tradfri app does not seem to allow the adding of devices to more than one Amazon account.
I don't quite understand why smart home devices aren't shared with your entire household by default. Why wouldn't I want someone else in the house to be able to control the lights or any other device for that matter? Surely it would make more sense to share smart home devices by default, and in order to cover edge cases, allow users to make certain devices only for them on a case-by-case basis?
The same logic should apply to routines, speaker groups etc - it seems senseless to force people to set everything up multiple times.
But it's rather less beautiful when it only works in my account.
When I try to turn the lights on/off, half the time I get told "I couldn't find any devices called 'lights'" because the Echo is on his account. I then have to tell it to switch to my account before I can control them.
Julian, interestingly, I found my wife (with a separate amazon account part of our Amazon Household) is not able to see the new Amazon Smart Plugs I installed using my Alexa app. She can't see the groups or any of the Routines I created on her Alexa app using her iPhone. So she can't control the Smart Plugs, turning lights on and off, as I can.
But if I log into her account in the Alexa app on the iPad, I can see all the devices under the Smart Home menu. That same Smart Home menu is not available on the iPhone app.
The connection is there, just not available on the iPhone app. I'm guessing this will be an improvement Amazon will make at some point.