There is at least one other thread on this topic....
I've downloaded Android File Transfer on my mac, and I've gone into developer tools and changed the USB configuration to Media Transfer Protocol and have switched on USB debugging. Phone still not recognized by the Mac. Pretty ridiculous that I've spent the entire day working as a 'programmer' to get my phone to do something pretty simple.
Unacceptable that the phone and computer can't talk to each other. Pretty tired of having the various platforms being so proprietary. If there is someone who isn't just guessing but really knows how to fix this, it would save me from returning the phone.
Thanks!