I think it's funny how every week another ntrviewer replacement comes out claiming how much better they are than the previous one. With that being said this looks the best and has creatures I've been waiting for. Nice!
mine shows a grey window.
Welll yeah, it's is dark grey if you want to precise.
If you didn't try it yet, check out the Multiple Network Adapters Fix. If you didn't, I'll release an update soon which should fix that issue anyways.
Tested on New3DS a9lh + luma3ds. I got it working but with 6fps while kit kat gets 45-60 and it doesn't close when clicking on the X. I had to close the proccess by the task manager :\
That's because Snickerstream currently doesn't check for user input if it's not receiving any frames (check the known issues file). You can close it using the tray icon if that happens - but it's already fixed in a private version anyways.
Also, did you set the priority to the bottom screen? If so, that's a known issue too.