Problem wiith the definition of a new content directory

[paoloviv@gmail.com]

I use a TS-453A QNAP NAS. As shown in the following screenshot, all I have stored on
the server is in a directory called NAS (attachment 1)    
The subdirectory "11 -HQ MUSIC FILES" contains all the relevant audio files. If I copy this subdirectory within Multimedia, which is the default path for MinimServer, everything works just fine. However, when I try to readdress the search to the NAS directory following the instructions to do so, I get an error message (attachment 2)    
What am I doing wrong?
Thanks for helping