I had the same problem with ARMA3. I found a solution wich worked on Jester814’s Youtube channel. The problem is linked toa missing parameter in the ARMA3’s profile.
Here it is copy/pasted from above source:
-Go to your user.arma3profile file. Open it with a notepad application
-Find it in C:users/username/documents/arma 3 profile/username.arma3profile
-search for “freetrack”
-Make sure Freetrack=1 (If Freetrack=0 then this is 99% why your EyeX isn’t working)
-Save, Close, and start ArmA, hopefully this fixed your issue! Enjoy!
This should work across all Bohemia titles.
Thanks a lot Jester814.