Hi @tigamendonza, sorry to hear about your troubles. Unfortunately, as you are using a Tobii Eye Tracker from the Tobii Tech Business unit in conjunction with an SDK from the Tobii Pro Business it does complicate the issue of the correct team to speak to, but I will try to offer what advice seems relevant.
In general, NaN values may be produced when the Eye Tracker is connected properly, but there is some issue in capturing the eyes, either due to blinking, strong sources of infrared light nearby (open Windows, spotlights, etc) heavy makeup, facial piercings, etc or simply when the user is outside the range of the tracker itself.
Assuming you check the environmental conditions are properly adjusted, then I would recommend you perform a test over a couple of minutes by focusing your gaze over a number of pre-defined points (say 4: one at each extreme) on the screen, ensuring the gaze never leaves the monitor area.
Have a look at the resultant output. If the Data contains a significant amount of NaN values, this would indicate either some environmental condition or issues with the user themselves and so would recommend you to run the test again on another user.
For cases where No GazeData (not even an empty object) when expecting a datapoint to come in via GazeDataReceived: This could indicate a possible hardware or connection issue however I would investigate all these options first and report back. Again would be useful to know what fraction of the total output we are dealing with here.
Something also worth trying is to run these screen test program using the Tobii Core SDK which is in fact designed for operation with the 4C. It would be interesting to see if the same NaN/NoData issue persists or not.