"Whoops! Cannot reach User Daemon." when attempting to use NordVPN

I'm in China and on Ubuntu 16.04 and have installed NordVPN through apt. When I run nordvpn login or nordvpn X I just get:

"Whoops! Cannot reach User Daemon."

I also tried running nordpnsd which runs without output and then terminates and then nordvpnud. This runs without output until I try "nordvpn login", at which point it goes:

2019/05/30 12:51:49 [Error] rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = "transport: Error while dialing dial unix /run/nordvpnsd.sock: connect: no such file or directory

If you're seeing Daemon is unreachable, is systemd running? or Whoops! Cannot reach System Daemon. your NordVPN daemon isn't currently running.

To start the daemon, and have it also enabled the next time you boot, run:

sudo systemctl enable --now nordvpnd.service

To just start the daemon once and have it disabled the next time you reboot your system, run:

sudo systemctl start nordvpnd

NordVPN seems to require two daemons: nordvpnsd and nordvpnud. These are provided in the install package and reside in /usr/bin. They are binaries and not scripts, so can't be modified.

The error message probably means that the daemon was not found in the user context. The reason is, I believe, that nordvpnud is supposed to be run per user. I would suggest to run it yourself, rather than during startup.

If you wish to run it during startup, use the chpst -u:

exec nordvpnsd 2&>1
exec chpst -u <user-account> nordvpnud 2&>1

As I'm not using NordVPN, I cannot go any further than that. For more information, see this post.