lkp If I remember correctly, when I wanted to use an openvpn config file via the NetworkManager, I had to download the following package:
Also, you can verify that the openvpn config file that you downloaded has no issues, by running:
sudo openvpn /path/to/the/openvpn/config/file.ovpn
By running the above command, you should be prompted to enter your VPN credentials and after that, you should be logged in to the VPN server.