Sensor malfunction of ventostat 8000

The light on the unit is no longer flashing green, it is flashing yellow. When the room gets to be a certain humidity the heat drops out completely.

Welcome to the Digi-Key TechForum cintron.m
What Digi-Key part number is this on?
I do not know what item you are talking about.

235-1715-ND

The T8200 (235-1715-ND) per this document would be a non-display device that provides an analog-output CO2 signal and independent thermistor for temperature measurement–this model would not appear to provide any humidity detection function.

The complaint then, that When the room gets to be a certain humidity the heat drops out completely. would seem to suggest some sort of problem with the larger climate control system of which this sensor is part, with the yellow flashing LED on the sensor being a likely symptom of that problem. For this reason I would suggest that contacting a local HVAC service technician may be a more appropriate means to a remedy.

Please feel free to offer additional details if it seems that my understanding of the situation is incorrect.