The terms “Primary” and “Secondary” may be misleading here, let me try to make it a little clearer :-
In Windows 10, I right-click on the desktop, select “Graphics Options” from the context menu, then “Output to”, then “Extended Desktop”. From here I have two options 1- “Built-in Display + Digital Display” or 2- “Digital Display + Built-in Display”
I normally use option 1- “Built-in Display + Digital Display”.
The EyeX is mounted on the digital display which is plugged into my laptop.
When setting up the EyeX I ensureded the “Display Setup” was showing on the digital display and adjusted the two markers on the screen to match the lines on the EyeX device.
The EyeX setup works correctly, I popped the dots and everything – all on my digital display.
So in your comment “The EyeX must be mounted on your primary screen“, I assume you mean is the EyeX attached to the monitor that I am looking at?
And my answer is obviously yes, because otherwise I wouldn’t have even got the EyeX software properly configured.
However, in this configuration, ED is configured to run on what _it_ terms as the “secondary” (which is the digital display and the one that I’m looking at with the EyeX attached), and in this configuration I got up/down headtracking, but no left/right head tracking.
Now, by changing the windows configuration to option 2- “Digital Display + Built-in Display”, and Elite Dangerous to run on what _it_ terms the “primary” (which is _still_ the digital display and the one I’m looking at with the EyeX attached), I get both up/down and left-right head tracking in E:D
The only other interpretation that I can make on your comment about the “The EyeX must be mounted on your primary screen” would be that the EyeX must be mounted on the laptop display itself, which is clearly not the case, as the EyeX itself works perfect well in the digital display.
So, I can only assume that something in the EyeX or ISE software is not properly catering for the Windows option 1 configuration.