After applying recent security fixes for Windows 8.1 (https://technet.microsoft.com/library/security/MS15-011) my Cisco ANYConnect client failed to load. Error:
Cisco AnyConnect: Failed to Initialize connection subsystem.
I’m not sure what it is about the most recent security updates that made it stop working, but I found that by setting it into Windows 7 Compatibility mode the issue was resolved.
The registry hack for doing this was:
Add a string value with the string name set as the full path to this file:
C:\Program Files (x86)\Cisco\Cisco AnyConnect Secure Mobility Client\vpnui.exe
Then set the string value to:
After making the registry change, right-click the AnyConnect icon, and choose Quit:
Then re-launch the AnyConnect client. and all seems to work.