Domain mapping plugin not working

I have a mulsite set up with blogs on subdomains and I am trying to get the domain mapping plugin to work.

DNS and web server is setup correctly and the mapped domain routes correctly to the wordpress install, but there is reroutes to maindomain/register.

I have trawled the support threads for solution, but so far I have not been able to find a solution.

- Sunrise.php has been copied to wp-content
- Sunrise is referenced correctly in wp-config
- The current_site lines have been commeneted out in wp-config
-The mapping appears in the database