When Android switched to MTP (which I have disliked since the change) I had to download the Samsung USB driver for mobile phones. That fixed the problem, but now it won't recognize it at all. I think this is due to a recent update of the Android system. I downloaded a newer version of the driver from Samsung and that didn't fix the problem. I don't know what to do other than get a new computer (which I have been planning to do anyway).