If you cannot access your website at the new URL, you need to remove the reference to the old domain name and save the new domain name in the wp-config.php file.
To edit this file, you need to access the webspace with an FTP program or the WebspaceExplorer. You can find the login data for your FTP account in IONOS under Hosting > Manage Webspace > Secure FTP Account.
You can then edit the wp-config.php file. Paste the following entries at the end of this file and replace "http://www.new-domain-name.com" with the new URL:
- define('WP_SITEURL', 'http://www.new-domain-name.com');
- define('WP_HOME', 'http://www.new-domain-name.com');
These constants overwrite the entries for the previous URLs in the database. This also applies to the URLs that were defined in the WordPress back-end system.