CHANGE, RISING, and FALLING Interrupts not triggering on Due Atmega328

I have setup an optical RPM sensor which is triggered when it detects a reflective strip on a rotating shaft. I have attached the interrupt to pin D22 of the DUE. Although the switch is triggering properly (at which point it returns 0V instead of 3.3V) it is not triggering an interrupt when set to RISING, FALLING, or CHANGE. However, when configured for a LOW interrupt, it works properly.

Unfortunately, I cannot use LOW because if the rotating component stops rotating when the interrupt is active, it continually runs the counter function.

What am I doing wrong?

EDIT: this is the sensor in question: http://www.mcmaster.com/#rpm-sensors/=x4jwvr EDIT2: here is the sketch I am running: https://github.com/mutrac/MR16/blob/master/sketches/TCS/TCS.ino

You shouldn't use all upper case for variable names, the convention is that such names are constants - you will cause a lot of confusion that way.

Anyway I can't see anything wrong with the code, you are likely missing pull-ups on the sensor output, open-collector outputs are pretty universal in industrial sensors so as to be voltage-agnostic.