I was just about to post about this. I am having the same problem on a Shield TV.
Streaming from a PC / Steam enhanced edition, I can start the game no problem, and it recognizes input from either controller (in my case, it's one steam controller and one Xbox 360 controller). The trouble is that it doesn't seem to recognize that they are separate controllers, and so it won't give me the option to create a local coop mode.
I suspect this would require a patch of some kind to fix and it's a fairly specific hardware issue, but streaming is becoming more popular - and you guys (Larian) have already done so much good work to make this game accessible, I guess I'm just hoping to take advantage of your commitment in expanding it to those of us who no longer have a PC in the living room!