Maybe something has changed in rc release, try to ask on opentrack forum or report a bug.
ED officially supports TrackIR only so headtracker.dll for opentrack/freetrack/FTnoIR are comunity compiled. There are four or five different versions, the most up to date is compiled by 'samtheeagle' that works with Huey, search the forum for the thread.
There is also one on FTNoIR website.
Basically you have to try them all...
In my case none of various 'samtheeagle' versions worked on my PC, I didn't even get headtracker column in settings. FTNoIR version worked but was crashing DCS. I searched eagle forum for couple of days and found one outdated dll that works fine (made by 'prok' I think).