VirnetX needs to install a system extension on macOS to function as a VPN provider. This requires some user interaction to allow the extension to be installed.
After installation you should see a popup dialog similar to this (note: screenshots were taken from macOS Monterey, older versions of macOS may look slightly different)
Select “Open Security Preferences”. If you select “OK” you can get to the Security Preferences from the “System Preferences” tool.
The Security Preferences panel will look like this:
In order to allow the system extension you will need to click on the lock in the lower left corner if it is not already unlocked.
Once unlocked you can select the “Allow” button
The system extension will then be installed. The operating system will then prompt the user to allow the VPN configuration:
If you mistakenly select “Don’t Allow” you can restart the application to be prompted again. To do this, select the VirnetX logo from the toolbar, then “Quit” and reopen the application.
Once the VPN has been allowed you will not need to do this again.