I have tried various approaches to resolving this problem and I'm going mental. I followed the common recommendations (repeatedly), like the Kies uninstall, and restarting my Macbook. MTP is selected as well. I use the samsung cable that came with the phone but I still can't figure out why it won't work! Been trying to transfer music to my SD card on the phone but I always get the this message, "Can’t access device storage. If your device’s screen is locked, disconnect its USB cable, unlock your screen, and then reconnect the USB cable."