We apologize for the trouble logging in to the VyprVPN service via CLI on your 18.04 version of Ubuntu.
We're aware of this issue with these newer builds of Linux. Our guides were configured using Ubuntu 16.04.1 While they might work with newer distributions, they are currently unsupported. Our Dev team is looking to add support for these newer versions in the future, however we do not have an ETA at this time.
We would suggest either using one of our manual OpenVPN or PPTP configuration guides linked below. If you are desiring to the CLI in the mean time you would need to install Ubuntu 16.
If you are in need of further assistance, please reach out to Support, they're available 24/7 including holidays! https://www.goldenfrog.com/contact-support