Help needed - accessing HDX drive via Wifi

My HDX (2010 vintage) is connected to my Wifi - I use n-serve to control it and that has always worked well from a number of devices (iPhone, iPad, mac etc.) I can also 'see' the drive from my MacBook and in the past have very occasionally played the files locally by copying the files in an album into Fidelia on my Macbook then playing through headphones.   I have recently got hold of a Chord Hugo headphone amp/DAC and I am now much keener to use this route.  My problem is that my Macbook only 'sees' the HDX on the network (and shows it in the Finder window under Devices) intermittently.  Sometimes the drive is there; sometimes it is not.  I know the HDX is always connected to the Wifi because when I use n-Serve it works fine.  Any clues what might be going on and if there is a setting on the HDX (or indeed on the Mac) to make sure that the HDX will always be visible?