I recently installed NordVPN on a machine with a dual-boot (Win10 + Ubuntu) and all was good until I tried to uninstall. At the point I lost the ability to connect the internet, not with the WiFi and not with the cable. I had a long exchange of emails with their support team but they didn't help to solve the problem. In the end they just told that the problem is with my OS and they can't help me in any way. They made install and re-install the package a number of times, made me change my DNS servers, disable IPv6 and reset the NetworkManager. I'm not expert so I followed blondly their instructions.
I'm not in the position to simply re-install the OS as I would have done normally, so I hope that someone can help to fix it.