It was the disk that had changed named.
I.e this line in fstab :
The device /dev/disk/by-label/pgnas2 does not exist
if i change it in fstab to :
and do a mount -a
i then have :
My disk mounted (last line) and i can access the files on the nas
however , i still have the same problem in the omv gui
i can still not see that filesystem mounted in the gui.
but perhaps you can help fix that last bit?