Help needed to understand the message and tune the query which is causing high cpu/io

I see this message in the  OEM sql advisor recommendation :- The optimizer could not merge the view at line ID 2 of the execution plan

the sql which is causing high cpu/io is, how to go about finding what is the issue and fine tune this?

SELECT *
FROM
(SELECT /*+FIRST_ROWS(10)*/ *
FROM VERIWISE.TB_EXT1_EVENT A
WHERE A.IS_PROCESSED = 'N' AND A.DEVICE_ID = :B1 ORDER BY 1)
WHERE ROWNUM <= GET_PARAMETER('PKG_GSMD200_MESSAGE_DISPATCHER', 'EVENTS_LIMIT')