@grant [Tobii] I have the exact same problem. Alienware 17 R4 with the QHD screen. The error message I get from the Tobii taskbar app is: please enable the tracked monitor. So Windows Hello is only working right before the laptop switches over to the external screen. After that Tobii is off.
The laptop is connected to an external monitor (LG 29UB67) through displayport but in this use case I disabled the laptop screen and work on solo external screen, but the IR camera is then off (no flashing red lights visible). Is this a hard limitation that both screens need to be enabled for the IR camera to work?