Reason 1

Adding attribute AnonymousAdminLookupEnabled="false" in the SecurityConfiguration tag of WebLogic 8.1 config.xml restricts MBean details from getting accessed from remote machines without authentication.

Solution

Set the attribute value as false. 

For more information, visit http://e-docs.bea.com/wls/docs81/config_xml/SecurityConfiguration.html#AnonymousAdminLookupEnabled

Reason 2

In the trial version of WebLogic, connections are restricted to a maximum of 5. So the request from Applications Manager might be blocked.

Solution

Try restarting your WebLogic instance and ensure that Applications Manager collects data before the limit of 5 connections is reached.

Reason 3

The proxy server is blocking the connection to the WebLogic server. The proxy server might have been configured to allow only HTTP requests.

Solution

Contact your system administrator.