base_url does not work

Please, check the link that is used for redirecting the user after a successful login.
Does it point to the old url (hard coded)?
Also check the application/config/routes.php file.
The mere fact that you can reach the correct login page, indicates that the base_url() setting itself is working correctly.

Hello, Wouter60,

Thanks you very much for your reply. The problem is fixed, it was an error in the .htaccess file.