Warning You Do Not Have Access to the Administrator Section of This Site

• Step 1: Check if the user is really an administrator: In many cases, this error happens when the person is trying to login with a user who’s not an administrator (usually this happens when the person has two users on the website, and he’s logging in with the wrong user) or who’s no longer an administrator (someone might have revoked administrative access for that user). Checking if the user is an administrator is easy – all you need to do is to check if the id of the user is assigned to the right group in the table jos_user_usergroup_map (replace jos with your table prefix) usually it is 8   If all is OK (the user is assigned to the right group) then we move to the next step… (If not then we fix the problem)
• Step 2: Check if the ACL tables are not corrupt: This is where it gets tricky since Joomla’s ACL tables are not that easy to understand. However, if the login problem is because of ACL corruption, then in 99% of the cases the error lies somewhere in the jos_viewlevels and/or the jos_usergroups tables. We suggest that you look at a clean Joomla database and compare the two tables of that database with those in your website’s database. If the ACL tables are corrupt, then we manually fix them (fixing these tables should only be done by an expert) – if not, then (you’ve guessed it!) we move to the next step.
  
• Step 3: Check the jos_assets table: If all else fails, then (sadly) the problem almost certainly lies in the jos_assets table (which is, by far, the scariest table in Joomla – because a simple mistake in that table can cause a total collapse of the website). The two most common causes in the jos_assets table that might lead to this problem are:
  
  1. Missing entry for the com_admin row.
  2. Wrong rules field for the com_admin row. The rules field for that row should just contain “{}”. (two curly brackets)