Originally Posted by gunner1937
As surprising as it might be I did read the post
My answer is based on my own experience. The Nexus 7 was seen in PTP mode but not in MTP.
To address the issue, after a thorough reading in the XDA forum and thanks to the knowledge of our Forum members, I updated the SDK manager and re-install the drivers.
Hope I answer your concern.
This is 99% a driver issue.
I had a similar experience when first setting up my n4.
Debugging on = adb but no mtp
Debugging off = not and obviously no adb
I uninstalled the adb drivers where possible.
Plugged in with mtp mode on and debugging off
Let it automatically install mtp drivers
Switch debugging on
Wait for it to install what it can by itself then manually install the adb driver
Results in fully functional adb & mtp
Sent from my Nexus 4 using xda app-developers app