I have a domain with a joomla site updated and SCP installed and running just fine. The domain let´s call it mydomain.org
Then i have other two domains registered with another registrar lets say mydomain.mx and mydomain.net.
I have set up a redirection for both domains directly from my registrar, i mean i didn´t change the ns servers, and just apply a simple redirection to my primary domain.
So mydomain.mx redirects to mydomain.org also mydomain.net redirects to mydomain.org
The redirection take place but i am getting an error page
I think that the HTTP Headers protection config could be causing the issue, but it's odd because I also have redirections to my domain with headers protection applied and everything works fine. Try commenting the lines of the .htaccess protection related to that feature and try again.