Unable to access Stat Agent when doing test connect from stat windows client (4255513)

After upgraded to 5.6.0, I am getting the following error when highlighting multiple Oracle apps db environment to do test connect:

Unable to access Stat Agent

Also when doing test connect from stat web, the status of the test result just say testing and it's never return the OK message.

USE_TNS entry column was blank

1. Go to Tools | Table Dump Utility and query for SELECT * FROM STAT_PSDB_CONFIG

2. Pay attention to the USE_TNS column to see if the value is blank. If it is blank then go to step 3.

3. Have the DBA run the DML below:

UPDATE STAT.STAT_PSDB_CONFIG

SET USE_TNS = 'N'

WHERE DB_CD='ENTER_DB_CODE';

COMMIT;