There are a couple of possible explanations for this.
- Your site may be configured to do so. WordPress, for example, may default to using the wrong name and needs to be manually informed under the General Settings in the WordPress Admin panel sidebar to use your real domain name. If the General Settings tab is unreachable, you can also change the site name from the command line with the commands:
YourPrompt$ wp option update home https://www.example.com/
YourPrompt$ wp option update siteurl https://www.example.com/
- You may be entering an invalid directory URI or something else that causes the network to redirect you. In this case, the server may not be using the name you expect in the redirected URL. (This primarily afflicts sites created prior to April 6, 2008.) If you have problems of this nature, make sure you have appropriate canonical name settings for your site.