[Building Sakai] Can't find user when grant ability

[wendy lee]

hi, all

I want to grant admin role to someone. So I edit realm "/site/!admin" and click "Grant Ability". Yet I can't find my user inside the "Set the Role for this User" page (!admin-355).
I am sure the user exists and I had successfully granted roles to somebody else before. I try to edit other realms and can't find users too. Nothing reports in tomcat log. I want to debug sakai.realm codes, but I am not sure where the code is. Can you help me?

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 wendy lee