If you haven't discovered it yet, go to settings, storage and the 3 dot icon upper right will change between ptp and mtp modes. In windows control panel, system, show all devices, and see if it says android composite driver. You can delete and let it reinstall when you plug in the nexus but first try rebooting the tablet while it is connected.
Also you may need to toggle off USB debugging in developer options on the nexus as that may be loading adb drivers instead of picture transfer protocol or media transfer protocol drivers. Ptp mtp.
If you still have trouble, I'll go find the android SDK driver link.
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