Issue with communication to the Inventu Metering Monitor
Your Inventu Viewer License is based on a Metered number of Concurrent Sessions or Users--Communication with the Inventu Viewer Metering application is required or your license cannot be extended past the minimum initially defined.
Ensure that your server has HTTPS (port 443) access to https://inventu.com. This will require a Firewall configuration...you can test yourself on the server by accessing https://inventu.com with a web browser.