During Webui setup (Services, HTTP/HTTPS tab in the admin console), the Test Connection process generates a failure. This is most likely due to IIS conflicting with the Webui.
Cornerstone/Titan uses proprietary webserver code to facilitate webui functionality. IIS is not required. In fact, it is recommended that you disable/remove IIS completely from the server. The reason is that IIS tends to "steal" port 80 and 443 for all the IP addresses configured on the server. There are two other work arounds for this situation (other than removing IIS completely).
1. Set either the Webui or IIS to use ports other than 80 and 443. It will be more efficient to set the webui this way since IIS does take those ports for all IP addresses.
2. Use the ListenOnlyList registry setting to force IIS to use only a specific IP address(es). Then, the Titan/Cornerstone server can be set to run on an IP address not listed for IIS use. The link below outlines the implementation of the ListenOnlyList setting.