Unable to get interrupt polling example to work on MCP23017 module

I'm trying to get the interrupt polling sample code on the MCP23017 module (DFR0626) page to run. I have the module wired to an Arduino Uno with this wiring: D -> A4, C -> A5, + -> 5V, - -> GND. The button input example is working with this wiring (button is connected to GPA0, and to VCC on the module), except that "Button Press" is printed when the button is open, and nothing printed when the button is closed. When I try to run "Sample Code- Interrupt Polling" with exactly the same wiring, I get no printout at all. I have tried the button on GPA0, GPA1, GPB6 and GPB7 with button connected to VCC, and also with button connected to GND. None of these produce any output. Help!!