downloadWhy can't I download this file?
Even though you see the message that installation was successful, VPN connections to NetScaler Gateway will not work.
This issue doesn’t arise if you upgrade from older Mac OS to High Sierra because the extensions were already approved during the previous plug-in installation on older OS.
Solution
As per the suggestion in the popup, navigate to System Preferences > Security & Privacy and allow the blocked extensions. If the problem persists, re-install the plug-in.
Note: You might or might not get the registration blocked message.
Citrix Workspace High Sierra
Problem Cause
macOS High Sierra has introduced a new feature that prompts the user to approve new third-party kernel extensions.
Citrix Workspace Requires Os X 10.13 High Sierra
Additional Resources