achtrade
Hi
Open Joomla global configuration > system > turn off URL rewrite.
Joomla use index.php in the URL turn on the URL rewrite option need rename htaccess.txt file to .htacess.
As you have not change, the page will not open.
+ check the configuration.php file in the site root folder and see the live site URL you have set there.
As it show a wrong domain name.
If issue remain same kindly submit the site temp super user login in edit fields options for staff.