After update my site isn't redirecting to WP theme

I’m confused: After a recent update when I enter my domain robertpetkoff.com it redirects to my very old website and not to the new site created with your theme. I have another domain (petkoff.com) which is an add-on domain to robertpetkoff.com and it shows the site just fine. I know that it is pointed at my wp directory. How can I fix this? I assume it’s something to do with my index.html file but I can’t figure out what to add to that file to direct traffic to robertpetkoff.com/wp.