What OS are you using?
On debian/ubuntu you have the file /etc/apache2/conf-available/dolibarr.conf where you change the alias option. After restarting apache with “systemctl restart apache2”. The change is loaded.
Also you need to change in /etc/dolibarr/conf.php the option dolibarr_main_url_root, this tells the correct setting to Dolibarr.
