That's because the login link you were using is probably
domainname.agentfire.com/wp-admin/
When your site goes live, you lose the '.agentfire' part, so the login link would be
domainname.com/wp-admin/
That's because the login link you were using is probably
domainname.agentfire.com/wp-admin/
When your site goes live, you lose the '.agentfire' part, so the login link would be
domainname.com/wp-admin/