Thank you for your support.
hosting account: lucidpad
Main Domain: lucipad.heliohost.org
Now I found this problem always happen when i attempt to log in cpanel (Not very sure).
The Wordpress have been installed and running well, but I remember that i deleted some files/folder under this domain folder.
I tested this again, when the following addon domain occur error, another(http://lucipad.heliohost.org/jianai/) seems working fine.
sub user: luckid
Addon Domain: luckid.com
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I have copied the /cgi-bin and .ftpquota to this ./luckid.com folder, not work.