0 ORA-01045: user SYSMAN lacks CREATE SESSION privilege; logon denied

Somehow, my OEM seems to not able to connect to the database.  After I log in , it can see the database is open but not able to get the information.

I found the error message “ORA-01045: user SYSMAN lacks CREATE SESSION privilege; logon denied”.

After I grant the “grant create session to sysman” and bounce the EM. It just back to normal.

Still not sure how I get there in the first place.