hth = hope this helps
I'm no Mac user, so I cant tell from accurate (to you) practice.
But once I've mounted a NAS path, I could always read files - once I was able to see the directories.
I might not have had write access, but read was always possible when mounted successfully as root (usualy using CIFS, not sure if that applies).
Also, have a re-try with just
su as I'm not sure wether or not you had passed that dash, which would make
su 'adapt' partialy to the env of the user (kind of, lost in translation and memory).
Comes to mind, check your 'mount nas' options, they might 'provoke' list only.
Also, forgot to say earlier, please use ICODE (Icon: >_) for 'on line' commands, and 'CODE' tags (Icon: </>) for multi-line output, such as your initial post.
hth