The Database Status is Currently Unavailable

Sometime when we try to access EM webpage and receive below error. it is becuase of two most possible reason.
1. If SYSMAN ACCOUNT IS LOCKED.
2. If Database Server Currently NOT OPEN.

SQL> select account_status
2 from dba_users
3 where username = 'SYSMAN';

ACCOUNT_STATUS
--------------------------------
LOCKED(TIMED)

SQL> select status
2 from v$instance;

STATUS
------------
OPEN

"SYSMAN" account is LOCKED.

SQL> alter user SYSMAN account unlock;

User altered.

--Now try to access EM page.