I bet it is a 3rd party Firewall preventing the User from accessing the Files. Look into that, too.
First off, I'd create a Test-User with a password.
Give that User full access of the Video Folder.
Create the same User on the Dune, with that same password.
Start discovering Files. That's how I start, anyways.
See if any programs are installed, like
McAfee or Norton Security
Avast Internet Security, you know, the usual [email protected]
Un-install them all.
Give the PC and the Dune a static internal IP Address.
Start pinging each other.
Search the Dune by IP, not the Name.
I wish I could help, if you PM me I'd use TeamViewer to assist.
I'm a certified Network Tech.
Hope this helps.