Assuming the tire is still there
make sure the tire sensor is still on the tire too. How long have the batteries been in service on the tire sensors? I get about 2 full seasons out of a set of sensor batteries, but I remove the sensors each Fall and reinstall them each Spring......so a full timer probably a year+ I would expect.
Is the EEZ tire monitor scrolling through the tires OK and then when it hits the "missing sensor" tire you hear a short beep with no readings shown and then it continues on to the next tire? If yes, I find it is usually a battery starting to fail so the transmit distance is starting to be reduced to the receiver. You can verify the sensor is still good by moving the monitor panel closer to the dropped sensor. It should register again within a few minutes. If not then removal of the sensor and battery replacement usually does the trick. So far (several years now) we have never had a sensor actually fail, but like anything electronic they certainly can fail.