NFS permissions... again

Hi there,
Enjoying Volumio for several years now. recently I moved from Mac to Linux (Ubuntu) with my client. Volumio is running on a RPI2+. I am trying to mount my Ubuntu Music folder, but I don’t succeed, nor with CIFS, nor with NFS (which I would prefer).
My /etc/exports:

I tried also without the anonuid and anongid parameters.
My path in Volumio > My Music:

I tried with and without preceding /

In username and password I fill in my Linux user account.
Errormessage:

I cannot find any instructions about the pathname in relation to the exports path. However, I think there is something wrong with the permissions. The Data volume and its directories are rw accessbile for user friso (me).

Thanks in advance for any help with this issue. Since it is recurring on several forums I think there is either something wrong with the software or with the manuals and examples: they never seem to fit the situation at hand… Hope some of your experiences can help me out.

SOLVED: I came to this page with instructions:
https://help.ubuntu.com/community/SettingUpNFSHowTo
I did every step until “NFSv4 client”. I only changed path and filenames to my needs and situation. I then entered the export path in Volumio (/export/music) and then the magic happens.
My lesson: NFS is serious business: it is important to know what your are doing. SInce a lot of the answers on forums only cover parts of the solutions, reading these is not enough: a step-by-step instruction for NFS config is what you need.