Hi @scaustin34 and sorry to hear about your troubles and the run around you have received. The issue is that the Tobii 4C is part of the Tobii Tech business department whilst the Tobii Pro SDK is part of the Tobii Pro business department, where we each have our own unique support structure.
Accordingly, my suggestion firstly is for you to try (at least experimentally) running our own SDK which are designed for the 4C Range such as our new Interaction Library which has .NET bindings and you can download @ https://developer.tobii.com/consumer-eye-trackers-interaction-library/
It comes with a sample ready to run directly (We recommend VS2019 for this) and should allow you to quickly see if the NaN’s are appearing in the gaze stream here as well. If they *are*, then that may imply an issue with the hardware itself as Nan is returned when no eyes are found or there is some issues of connectivity.
Let’s go through this stage first and report back and see where we are. May I ask if there is a particular reason for using the Pro SDK .NET Bindings? Certainly, if you are using the Tracker for analysis or long term data storage, you will still need the analytical use licence, which I assume you have, but you can still use another SDK if suitable. And as the Interaction Library support C#, you should hopefully not face much issue in code transport.
Thanks for your patience whilst we try to get to the bottom of the issue.