I have serveral times lately come across some user account related problems on Joomla 3.x. Typically this is happening on sites that I have migrated from Joomla 2.5.x, so the problems might be ocurring on that version as well.
The symptoms are the following:
1) A user cannot login to the frontend of the Joomla 3.x site. After entering the login details and clicking the login button, the user is simply lead back to the login screen, without being logged in to the site. (Funny enough, a superuser can login as normal, and does not seem to be affected.)
2) The other problem I have identified is when I try to add Google "2-factor authentication" for a user, and try saving this, then I receive the error: Save failed with the following error: You cannot remove your own Super Admin permissions
Basically the way to sort this problem is the following:
- You need to change a setting in the database. Use phpmyadmin which is provided on most Web hosting packages to access the MySQL database for your site.
- Locate the _assets table in your database.
- The first entry should be id # 1 and have a name of root.1 and a title of Root Asset.
- Edit this entry and change the lft column from a 1 to a zero.
- Save the change.
After performing the above steps I find that both problems above are gone.