Network Drive is in use, but don't have access to items, how to I disconnect?

The N: drive is already mapped to something.  You can either disconnect what is mapped to N: or make your new mapping to another drive letter.  The general format for mapping a drive is:
   NET USE driveletter: \\servername\sharename /PERSIST

To unmap a drive, use:
   NET USE driveletter: /DELETE

More info here: https://www.howtogeek.com/118452/how-to-map-network-drives-from-the-command-prompt-in-windows/

If the drive is mapped by GP, just right-click it, disconnect, then do a gpupdate /force from an administrative command prompt.

If manually mapped, right-click and disconnect, then remap the drive. As Paul said, the N: drive is already in use.

Possibly a conflict with a policy, you you use a policy to map a drive while you already have mapped it manually?  

is this issue solved?
I yes, you may close the question.

Thanks for your help!