Then the AnyConnect Secure Mobility Client Downloader dialog appears saying the AnyConnect client servic is not responding. And then the following alert appears 'VPN lcient agent was unable to send a success response to an IPC peer requesting the creations of a VPN connection'. It appears I have to restore back to Windows 8 if possible. Refer to AnyConnect: Corrupt Driver Database Issue in order to debug the driver issue. Disconnection or Inability to Establish Initial Connection If you experience connection problems with the AnyConnect client, such as disconnections or the inability to establish an initial connection, obtain these files.

Reference

When attempting to open the VPN client, the following error messages may result: 'Failed to load preferences,' or 'The VPN client failed to launch the client user interface application.'

Unable To Connect To Cisco Anyconnect Vpn Client

It appears that there may be corrupt preference files. If there is more than one user account on the computer, it is suggested to remove the files for each user account.
Since there are hidden files you will need to follow the instructions in Section A, then proceed to instructions in Section B below.
Section A
Windows 10 - Instructions to reach hidden files.
1) Access the Control Panel
2) Type 'folder' into the search bar and select 'File Explorer Options'
3) Then, click on the View tab at the top of the window
4) Under Advanced Settings, locate 'Hidden files and folders...'
5) Then, click on 'Show hidden files, folders, and drives'
5) Click on OK
6) Hidden files will now be shown when performing searches in Windows Explorer
Windows 8 - Instructions to reach hidden files.
1) Access the Control Panel
2) Type 'folder' into the search bar and select Show hidden files and folders
3) Then, click on the View tab at the top of the window
4) Under Advanced Settings, locate 'Hidden files and folders...'
5) Click on OK
6) Hidden files will now be shown when performing searches in Windows Explorer
Windows 7 - Instructions to reach hidden files.
1) Open Folder Options by clicking the Start button, Clicking Control Panel, clicking Appearance and Personalization, and then clicking Folder Options.
2) Click the View tab
3) Under Advanced Settings, click Show hidden files and folders, and then click OK
Section B
Windows 7, 8, & 10
1) Go to: C:ProgramDataCiscoCiscoAnyConnect Secure Mobility ClientProfile
2) Delete all the files in this folder
3) Go to: C:UsersUsernameAppDataLocalCiscoCisco AnyConnect Secure Mobility Client
4) Delete preferences.xml
5) Right click the Cisco icon in system tray and quit Cisco AnyConnect
6) Launch the VPN after deleting everything, put vpn.illinois.edu in the server window and use your NetID and password to log in via the 'Split Tunnel' profile. If you are planning to use Library resources you might need to use 'tunnel all'.