So I am not sure if this is a known issue.
I got the MiBox on it's launch day from Xiaomi directly for my girlfriend. She lives with a roommate and they don't share their netflix so the cast option is very important to her(absurd but whatever lol).
So for some reason she can't cast to the mibox unless she is signed into netflix app on the mibox itself. Is this a known thing and is there any way around apart from getting a chromecast itself?
Yea that seems to be the norm, and not just for Netflix. Youtube also will simply use the Youtube app to play. To me that is not "casting." That is telling another app, "yea go ahead and play this for me."
Yet for apps that are not on/available for the mi box casting works as expected. I can cast a chrome tab from my laptop and it certainly doesn't need Chrome installed on the mi box for that to happen. Or in the case of video, DirecTV Now: it works via casting and there isn't even an Android TV app available for it yet. I sure hope they don't change to the "run on app" method when there is. Ideally there should be a toggle for this, as in some cases it could be better to run the app on the Android TV box itself.
Try casting with screen mirroring, instead of casting through the app.
Iirc this is also an issue on the Nexus player so I think this may just be an Android TV limitation since casting boots up the native Netflix app and its already signed in. She may indeed need a Chromecast unless she can learn to live with split profiles on one account