If you encounter an error while attempting to access the CUPS web browser interface or you cannot access the interface, see Requirements for the CUPS Web Browser Interface to ensure that all of the requirements have been met. In addition, verify your browser's proxy settings to determine whether a proxy server has been configured. If so, try disabling the proxy server, then try again to access the CUPS web browser interface.
To determine whether the CUPS web browser interface is running, you can also attempt to connect to the CUPS port (Port 631).