With the correct IP and port address, the 404 error occurs when trying to access MVS Copilot from Internet browser.

Probably the copilot USS directory name is not found, due to a mismatch. For example, during the installation step, (into the A03PARM member) the Uss directory name has been defined with uppercase, whereas into the COPPARM file, the same name is defined with lowercase. (USS is case sensitive like any other Unix system.)