Not a solution I'm afraid, but a workaround in the mean time. Use AirDroid to transfer files over wi-fi.

 

The only thing I can think is that there is a problem with the USB port on the phone

I've had a few issues with USB connections but it has always been down to a dodgy USB cable. The phone has never been the problem (touchwood ).

If I were you, I would contact Google Support about getting the phone repaired.

 

It sounds like in every case, the mtp driver isn't installed or can't install. Let me look to see if I can find a manual install method. What os have your tried using?

 

You mention you've tried it in a USB 3.0 port? Do you have a USB 2.0 port you can try plugging it in to? I'm sure I read recently the phone has difficulty talking to PCS via 3.0 ports.

 

Last resort, in Settings, Storage tap the the dot menu and select *USB computer connection*. Try changing this to *Camera (PTP)* then reboot and try connecting the N4 to your PC. If you get any joy set it back to *Media device (MTP)*, reboot again and try connecting to the PC again.

 

Not sure if it was asked, but are you trying this with usb debugging enabled or disabled?

 

You should still be within your warranty period. With all you've done to diagnose, it sounds as if it's a hardware issue.

Your best bet is probably giving Google/LG a call I'm afraid.

 

I had to try try multiple USB cords until I found one that worked. No idea what was different about the cords.. but only one of the ones I own will work to connect my Nexus to my laptop.

If my memory is right, it's the USB cord that came with the phone.

 

The OP should verify that any case or skin is not interfering with the usb connection by not allowing a full seat, otherwise it appears that the factory usb cable is defective somehow, a bad wire-to-contact connection, broken wire or corroded/oxidized contact.

I've previously found a broken wire in an otherwise fine-looking cable, age unknown. A simple continuity test with an audible VOM was the tool used.