When browsing to the root URL of your DLP Enforce server (for example: https://enforce-server.yourdomain.net/ ) you receive a "Page cannot be displayed" or similar browser error. The HTTP error code displayed in the error is "400 Bad Request." Connecting to https://enforce-server.yourdomain.net/ProtectManager works normally.
On the Enforce server, make sure that the file \Vontu\Protect\tomcat\webapps\ROOT\index.html (on Windows) or /opt/Vontu/Protect/tomcat/webapps/ROOT/index.html (on Linux) exists and is a valid HTML file. As installed, the file contains a META tag that redirects to the ProtectManager servlet - if this file is removed or cannot be accessed, such as during an upgrade, the redirect no longer works.
You should also confirm that the tomcat/webapps/ROOT folder, and all subdirectories and contents, are owned and readable by the user account that is used to run the Vontu Manager service (typically protect).