Sometimes after adding a new domain, it starts mistakenly redirecting to another domain of your account if you link it to an existing website. To quickly fix this problem, take the following steps:
Go to websites page;
On the domain that is mistakenly redirecting to another website, expand its settings and choose "Unlink" option;
Confirm unlinking the domain (the domain will jump to the unlinked domains section);
Expand domain settings again and choose "Link" option;
In the appeared dialog choose the website from the dropdown that you have unlinked the domain from.
After a minute or two the domain should start working properly, and the redirection should go away.
Sometimes it happens that browser caches the redirection. Then clear browser cache and restart the browser.