Wp-admin hosted on different domain for SSL causes login loop with PHP sessions

We just implemented a wordpress theme called Answers, which can demo here live https://templatic.com/demos/?theme=answers. The theme was put on a separate wordpress instance, on a fresh subdomain.website.com.

Problem is, our web host manages databases, wp-admin, content, php server, everything on each dedicated server. So when you try to login at wp-admin, you actually get redirected from website.com/wp-admin to website.ssldomain.com/wp-admin, for security reasons. That’s all fine and dandy, however, this particular theme uses custom logins and php sessions for users to register to post questions or login to answer them.

Try registering or pushing login in the demo url i just provided and check the url out.

When I try to do the same thing at our instance, it goes in permanent loop until it finally hits a brick wall and returns this error –

This webpage has a redirect loop The webpage at https://subdomain.sslhost.com/?ptype=login has resulted in too many redirects. Clearing your cookies for this site or allowing third-party cookies may fix the problem. If not, it is possibly a server configuration issue and not a problem with your computer.

How could I work around this so that registering and login could be served in the same way as in the theme demo site? thank you !