I recently moved to Pi_AMD64 - the PC version I don’t know the exact name but NordVPN suddenly decided it could not connect. The error turns out to be something like this:
Cannot open TUN/TAP dev /dev/net/tun no such file or directory
Now this is way over my head (I’m sticking to particle physics and brain surgery from now on) but this fix works (found on StackXchange here: https://unix.stackexchange.com/questions/501403/tun-module-loaded-but-openvpn-dev-net-tun-no-such-file-or-directory
mkdir -p /dev/net
mknod /dev/net/tun c 10 200
chmod 600 /dev/net/tun
cat /dev/net/tun
I didn’t have a /dev/net/tun (the directory was empty) but this saved the day and my sanity.