So I had ordered some micro usb to usb c adapters from amazon (the brand is Aukey, 3 for $7) for the many micro usb wires I have so I can use my them with my Pixel and out of curiosity I attempted to do a file transfer from my imac (5k 2015 model) using a micro usb wire with the usb c adapter and it was SUCCESSFUL!!!!!!! Once I selected file transfer in the usb options it worked flawlessly!!! I transferred a few gigs worth of music without a problem, no errors and the screen even timed out. I guess Macs dont play well with the usb c wire from Google. Someone else give it shot!!!!