I followed the instructions from a closed forum entry on this and downloaded the installation file from the GitHub site. First of all it wouldn't work because it said a file was missing (from the requirements list). I removed that item from the stuff to copy and paste into the Terminal and it went in OK. However, when I R-clicked the new Nord VPN icon on the desktop I got this:
Did you follow this steps (if not remove your previous install and try this)
To install NordVPN GUI on Linux, follow these steps:
sh <(wget -qO - https://downloads.nordcdn.com/apps/linux/install.sh) -p nordvpn-gui
Open NordVPN from your system's application menu.
Log in to your NordVPN account.
Connect to NordVPN.
I'm guessing you mean this:
I didn't download anything from Github, though it's been several months since I did this and I can't remember the sources off the top of my head. However, despite also struggling to make NordVPN work, I got all my setups either from NordVPN or from Zorin's software interface. In your position I would clear whatever you've installed and start again with the NordVPN instructions. Sorry not to be more help, but If I can think of anything I'll add it.
P.S. I see that Nourpon has added advice which looks good to me.
Thank you for your prompt reply. I can't remember what I installed (I am a complete newbie with Linux and all this Terminal stuff tends to do my head in!!). Could you please tell me how to get rid of everything I've got so I can start again? Thanks.
Thanks for your quick reply. Yes, this is the sort of thing I want to see. I want to be able to see what country I'm logged in to. At the moment I can't get onto my online grocery site because it says I can't log in with the current server, and I can't find any way to change this. What you have shown me looks more like what I've got on Windows, and it also gives me the option to pause Nord VPN for a short period if I want to.
you need to find in your browser history what you install from Github
Unfortunately I'm a noob too... 
Google is your friend - look for instructions on listing your installed apps so that you can see the name of the Nord app, then use the purge command to remove it. Unless more experienced members can help in a more concrete way...
try this:
sudo apt-get --purge remove 'nordvpn*'
and after use the method I sent
You are an absolute star!!! After 2 evenings of frustrating struggle, this went through without a hitch and was easy peasy lemon squeazy. My online grocery store opened like a lamb and all is well. thank you sooo much. Navigating through all this stuff as a Linux newbie is a nightmare but you guys on the forum are such a help!
Thank you so much! You guys are a great help. I've now managed to do it thanks to Nourpon's instructions and all is well. I look forward to getting through the newbie struggles with Linux...