When installing the VIP plugin for IIS, the SYMCIIS module is not present when browsing the "Configure Native Modules" (step 11 under section: Configuring the VIP Integration Module for IIS).

VIP integration with Microsoft IIS

Microsoft IIS does not always display all available modules in the scrolling section, but the SYMCIIS module is present after the scrolling section. 

To select the SYMCIIS module, scroll to the last entry showing in the list and press the "down" arrow on the keyboard to scroll further (you will see the blue highlight line descend below the shown list). Then press "spacebar" on the keyboard to select the module, and finally click the "OK" button to accept changes and close Native Modules window. Now you should see SYMCIIS present in the list of Enabled Modules.