Keeps redirecting to primary domain

Hi, I added my DNS settings and my secondary domain in the server_name line of my Nginx config. If i enter my secondary domain, it will load the site, but at the primary domain (that is, the primary domain shows in the url field, not the secondary domain). Do you have any suggestions for why this might be? In the “define your mapping” section I simply added a top level secondarydomain <=> primarydomain mapping.