How to see log of nmcli “Network connection failed :unknown reason”
Solution 1:
As mentioned on comments, you can grep --color NetworkManager /var/log/syslog | less or better use journalctl:
journalctl -u NetworkManager.service
-u,--unit=UNIT|PATTERNShow messages for the specified systemd unit UNIT (such as a service unit), or for any of the units matched by PATTERN. [...]
Hardly your country can block the use of OpenVPN. They probably block IPs, ports, unless they use advanced Deep Packet Inspection (DPI) techniques.