Cannot acces as a user of the site created in WSP

Hello,
I am getting the following error message when try to log as a user of the site created in WSP. I can’t access it while access is denied during the login. What did I wrong? Could you provide me the resolution to fix this error? I would be grateful to you for any assistance. Thanks in advance.

Error: Access Denied
Current User
You are currently signed in as: z51/_103222sp_admin
