Why do I get the “System Extension Blocked” message?
Since the macOS High Sierra 10.13 introduction, all newly-installed third-party kernel extensions (KEXTs) require manual user approval before loading. When a request is made to load a KEXT that the user has not yet approved, the load request is denied and macOS presents the alert.
As FlexiHub for macOS contains a number of KEXTs, a manual approval is a required condition for the proper functioning of the app.
To approve the KEXTs used by FlexiHub for macOS, please go to System Preferences → Security & Privacy and click the “Allow” button.