Here is a photo of the plug attached to my camera. You can see it is firmly seated as far as the metal ring on the mic plug will allow.
The mic appears to work as advertised, my computer works, and the camera's built-in mic works, so it seems we have narrowed the problem to the connection between the mic and the camera--specifically the seating of the mic jack into the camera (assuming the camera's mic input is not faulty).
Thank you to everyone who has attempted to assist me with my problem. I will try to locate an adapter as described by rawr. I will report back any success or failure I encounter.
A.D.