AFAIK it should not make any difference what filesystem you have on your NAS, as Volumio is not accessing the filesystem of your NAS directly. Volumio uses the CIFS or NFS protocol to connect to your NAS and acces your data.
So please explain in more detail what your have done, screenshots or pictures would help.
Did you create a CIFS or an NFS share on your NAS?
When you attached the NAS CIFS or NFS share, which parameters did you use?