Diagnostic Test Error Occurs

Diagnostic test, error occurs: Please change the log level to DEV and re-execute the test to get more details

EBS Version:12.0.1
Platform: IBM AIX on POWER Systems (64-bit)

Execute following action plans, still can not fix:

a). Login EBS as SYSADMIN
b). Switch to responsibility 'System Administration'
c). 'Oracle Applications Manager' -> 'Workflow'
d). Select 'Site Map' on left top region
e). Select 'Administration' tab
f). Select 'Applications Manager Log' link in 'Others' block
g). Select 'DEV' radio-button, and click 'Go' button
h). Restart EBS server
i). Now rerun the diagnostics and retest the issue

Please HELP~~

Thanks,
Jackie