Have you installed the library?
I'm still trying to find it.
I strongly suspect your application doesn't need any interrupts. Only use them if you are confident you can debug the complex problems they can cause. As you started by putting Serial.print() statements in your ISR I suspect you are very new to this.
I'm creating a cnc machine that uses the arduino to read g-code using code from MargianallyClever.com
The way the code is written, it waits for the stepper motors to completely go through all of the steps before reading anymore information from the serial port.
I want these momentary switches to stop the motors (which are driven by ada fruit motor shields) when triggered.
I've tried adding code into the loop but it doesn't work.
I tried using the basic interrupts on the Mega that are built in and that works but I want to shift over to different pins to trigger the interrupts.