Image Mate software not detecting Elmo MO-1 document camera

I am a tech coordinator for my district. I have a MacBook Air OSX 10.10.5 and I have installed the Image Mate software to use with my ELMO MO-1 document camera. The first couple of times I connected the doc cam, and launched the software it worked. Worked meaning, the software recognized the USB cable was plugged in and the image of what my doc cam was seeing was also displayed on my desktop. Now whenever I try to launch the software it says "no document camera connected" or something similar meaning, it can't "find" it. I have called the ELMO company and they suggested that maybe the computer had another application using the camera, therefore the image mate software couldn't locate the doc cam. There are no other programs running. I spent 51 minutes online with Apple and even a senior adviser could not help me. If we launch photo booth or Face Time and switch to the MO-1, we can see the image. So, it has to be the Image Mate software but the ELMO company is of no help to me. Just looking for suggestions from anyone at this point before I advise the teacher to send back the doc cam.