Thanks for the assistance. I had been using example-3-forces but decided to dump my code and start again. I hope the image below helps to expose the issue. The only changes I made are in green.
In response to constant pressure from my fingertip, I still only get zeroes for the contact bounding box coordinates:
There was a good stream of force data ("Total Force") in response to my fingertip press but I then commented that out to make it easier to search for non-zero bounding box coordinates, of which there were none.
Once this contact issue is resolved, then I look forward to finally getting the force array (for each of N contacts) after I change the mask and, of course, the loop logic.