ORA-12505: TNS: listener could not resolve SID

This error occurs when the SID specified in the connection was not found in the listener's tables. Check listener.ora in ORACLE_HOME\NETWORK\ADMIN on the machine hosting the MW repository. It should contain the following entries:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = C:\Oracle\RMW21_10201\home)
(PROGRAM = extproc)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = hostname)(PORT = 1521))
)
)

If listener.ora exists in the correct location and does not contain syntax errors, then this error indicates that another Oracle version is installed on the machine. Uninstall the Oracle version.