Nas netwerk drive mount issue

I am trying to connect a friends RPI volumio version to his NAS music folder (over teamviewer connection)
Unfortunately I have failed.

No network drive is found or accessible, below here the systems setup.

Network:
Volumio: ip = 192.168.1.203
NAS ip = 192.168.1.20

Volumio version:
I couldn’t find it’s version… but i just asked him to do an OTA update.
so this will be soon the latest version, doubt this will be an issue.

NAS:
Asustor, which is a linux based Nas (like most others) with latest OS update.

first issue i have is i am not sure what slashes to use…

I can successfully SSH into my NAS from windows desktop.
the local linux tree is volume1/Entertainment/Music
so when I add this i will get \192.168.1.20/volume1/Entertainment/Music
I doubt that these \ / slash setup is oke. but am not sure what to use? left or right slashes. and or if this is part of the issue at all. I tried all options, like this. all to the left, all to the right.

SMB NAS.
I setup SMB on nas ofcourse, highest version 3.0, lowest allowed version 1.0

I also tried adding vers=3.0 to the option field.

No matter what I tried, I failed to get connection to the drive.

Any thoughts on the issue would be appreciated.

Please try the following settings: