We understand your NAS is hardwired. What Steve is asking if you are unable to connect via SMB which is the most commonly used file sharing protocol.
Can you access the NAS web page? Or is the server completely offline?
You may want to open an SSH connection to the NAS and run the “top” command. See what your processor usage is. Perhaps your music server is eating a lot of processor time with lots of threads. The average CPU load line in top is the most important as it roughly shows the number of threads currently being processed. If the music server is taking a lot of resources, it could make the unit look like it is offline.