what domain registrar are you using? If you're using Cloudflare for your DNS settings and the domain is proxied, it will not work.
Edit: When I try to join the server using play.retroraids.com it says unknown host, which leads me to believe it's DNS propagation taking its sweet time. If that's the case then it should just automatically start working in 24-48hrs
Edit 2: This DNS Resolver Page shows it as forwarding to the correct address, so it's possible that it has just started working, so open cmd in windows and run ipconfig/flushdns then try to connect again