Davis might supply a "temperature test cable" - I don't know if they do that. You can manufacture one, if you are "technical" (or have a friend), by making a cable like the one from the t/h sensor, with a 10.2k ohm resistor between the red and green wires. That should simulate 76 degrees F (25 degrees C). If that makes the temperature work, it's likely that the ISS electronics are OK and the sensor needs to be replaced. If that does not make the temperature work, you'll need to replace the ISS electronics.