Users can not connect

[yosef]

Hello,

Upgraded my system from 2.5 to 3.1.

I returned the file settings.inc.php, and img folder.

The system seems fine

The problem that users can not connect.

Put username and password and it returns to login page again.

Has a solution?

Thanks.
sorry if my English is not 100%.

[MikeChoy]

Try deliberately key in a wrong user / password. If it returns error message, then check this
http://www.prestashop.com/forums/viewthread/63560/upgrading_prestashop/no_access_admpanel_backoffice_after_upgrade