Strangely, I tried with a different conf file (different NordVPN server) and it works, so perhaps it is server related.
This is the conf that gave me trouble:
osmc@Vero:/etc/openvpn$ cat se8.conf
# _ _ ___ ______ _ _
# | \ | | ___ _ __ __| \ \ / / _ \| \ | |
# | \| |/ _ \| '__/ _` |\ \ / /| |_) | \| |
# | |\ | (_) | | | (_| | \ V / | __/| |\ |
# |_| \_|\___/|_| \__,_| \_/ |_| |_| \_|
#
client
dev tun
proto udp
remote 193.105.134.166 1194
resolv-retry infinite
remote-random
nobind
tun-mtu 1500
tun-mtu-extra 32
mssfix 1450
persist-key
persist-tun
ping 15
ping-restart 0
ping-timer-rem
reneg-sec 0
explicit-exit-notify 3
remote-cert-tls server
auth-user-pass /etc/openvpn/login.txt
#mute 10000
comp-lzo
verb 3
pull
fast-io
cipher AES-256-CBC
<ca>
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
</ca>
key-direction 1
<tls-auth>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
c2bc3a0b361776230d70add89979dd4d
5ec2a8e7c12a8a65e3df4f25dc533283
7e993fd3894804d55755357247bfaf71
06f8df816cee258bb21c1800b25aacc4
70e654d81d5692219448f73ae748397b
977bf17a75517cb0b90165868fb2ccc3
06f33212215805dcca7594f5e45a0efe
46cb06d9aec58c00582bf6ebfda67236
5fe624fe37da830f4a9eacab244bea45
36d63347101bfb91510d4ce7e60dbc52
c260144d6d44024fffc21eb07501a7bd
9bbeab1f11b0c7b01750d3824f105ef8
25feca52a3b09d88cc6556c6c67bd112
900b8d23e4fb4ee75aff11e0ff5a7433
69c75326361dda146ac885477ee6d88a
ad887d29948a4482a9572e811107a7e0
-----END OpenVPN Static key V1-----
</tls-auth>
And this one just works, with and without login.txt:
osmc@Vero:/etc/openvpn$ sudo cat nl170.conf
# _ _ ___ ______ _ _
# | \ | | ___ _ __ __| \ \ / / _ \| \ | |
# | \| |/ _ \| '__/ _` |\ \ / /| |_) | \| |
# | |\ | (_) | | | (_| | \ V / | __/| |\ |
# |_| \_|\___/|_| \__,_| \_/ |_| |_| \_|
#
client
dev tun
proto udp
remote 185.212.171.201 1194
resolv-retry infinite
remote-random
nobind
tun-mtu 1500
tun-mtu-extra 32
mssfix 1450
persist-key
persist-tun
ping 15
ping-restart 0
ping-timer-rem
reneg-sec 0
explicit-exit-notify 3
remote-cert-tls server
#mute 10000
auth-user-pass login.txt
comp-lzo
verb 3
pull
fast-io
cipher AES-256-CBC
auth SHA512
<ca>
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
</ca>
key-direction 1
<tls-auth>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
ea06884eec88d28e3803967d7c40bec3
d5b2e9407e3418bc4e1f714960b7a393
7a1b5e12b6ffdd19ccc16c627d64f192
1f32277047ee3d4e4cf5222aff14e3ba
e7bff54df513cf59ec8d2d48cc5acade
3ab682e10c45e92fc855473d4a2fcd45
07c9218ece36e16f3b334420b6c62d2c
56403178ce72039927900eef0d99337f
d914604bc9609617bf642d3d5da6df0d
cf2c3f12c758a16464bb39fd21599348
ed9a7602b5523d9a7dd8fabc9733223d
4552933d865ca24100e4d19a5757b16a
26740c91080d64d275784e9b91cc025e
57cb920f44f95c2be09bb859abd8d336
5261f8e61e1946b3376e3aa0cfc3673e
1f88e4258a1dc288abcb051478390806
-----END OpenVPN Static key V1-----
</tls-auth>