No longer able to mount NAS drive

I am able to add the Music folder of my NAS to Volumio v3 via the UI, and if I ssh into my Pi I can navigate to /mnt/NAS/Prometheus and I can see all the files. However, viewing /var/log/mpd.log it is reporting:

exception: Failed to open /var/lib/mpd/music/NAS/Prometheus: Permission denied

I am using the correct username/password combination, and Guest has read access, but the above error occurs.

The weird thing is it has been working for months with the NAS without issue, but a couple of days ago it decided it just would not.

I am using Volumio v 3.759, upgraded today from the production release in the hope that it would fix the issue I am seeing.

i was using also at the past the NAS but also mine is not working now…
actually i changed some settings and it worked…

This thread might be helpful.

For an unknown reason, it started working again! No idea why. There was another nightly build of volumio in the meantime.

please tell me what you have done ? Since a few months my synology NAS does not work anymore with NFS protocol

Might be related to an older version of NFS on your NAS.
Try in the option field one of these:

nfsvers=2 or 
nfsvers=3 or
nfsvers=4