It should be \\ip of nas\
you are using //?
Also check if you can get to the web interface of the NAS over vpn. If so check the firewall settings of the NAS. I have a Synology Nas connected to my router and am able to get to it over VPN. Also turn the firewall off on windows and the NAS and the check the firewall on the router. If you can ping it it should be working. Also make sure you re-download the config file. Are you using windows? If so do you have the file discovery turned on?
Can you show a screen shot of your routing log from the router? And what ststic ip address are you using for the NAS? Can you access the NAS locally on the network without vpn?
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