You might be able to clean the sensor or LED(?) with a damp cloth. If it is paper dust fuzzing the signal, that might make it work again. If not, it might be a bad sensor or light, or a power problem.
Try rubbing alcohol on a cotton swab. Remember there is a sensor on both sides of the paper opening. If that does not work then you need new sensor. And IR sensor that you can make fit will work.
Answers & Comments
You might be able to clean the sensor or LED(?) with a damp cloth. If it is paper dust fuzzing the signal, that might make it work again. If not, it might be a bad sensor or light, or a power problem.
Try rubbing alcohol on a cotton swab. Remember there is a sensor on both sides of the paper opening. If that does not work then you need new sensor. And IR sensor that you can make fit will work.
One of the sensors is clear, the other has a blue tinge. Does this mean the blue one is "dead"?
That is the way the sensors are - one clear and one dark