The default port number for the EE and SE Administration Console is 4849; for the PE Administration Console it is 4848. Also note that the URL for the EE and SE console requires secure HTTP (https://servername:4849.), whereas the PE console uses standard HTTP (http://servername:4848). However, it could be running on a different port number than expected, either because it was intentionally installed there, or because that port was taken when the server was started.
Refer to Was the Server Started at the Expected Port? for guidelines on verifying the port on which the Administration Console is running, and be sure to enter the correct port number and HTTP protocol when invoking the Administration Console.