Reason: The required privileges are missing.
Solution: For creating new Oracle database monitor, you should have:
1. Admin privileges.
2. Minimum User privileges ->user with CONNECT and SELECT_CATALOG_ROLE roles. Some might try changing the SYS as SYSDBA for adding Oracle monitor. It is not possible to change the SYS as SYSDBA because Applications Manager uses JDBC for connecting with Oracle. In JDBC mode, changing of user into another user privilege is not possible.