Can't connect to server with domain

Hi all,
I set up my Mac Pro (3,1 -- El Capitan 10.11.6) with OS X Server 5.2 to run a file sharing service for when I'm away. It was working fine for a while; I could go into Finder, ⌘+K, afp://mydomain.com, and choose the volumes I wanted to mount. Now, for some reason, it won't work with the domain. I can use afp://MyIP, but not the domain that's linked. I can access my web server just fine, and System Preferences>Sharing shows "Other users can access shared folders on this computer, and administrators all volumes, at "afp://mydomain.com" or "smb://mydomain.com", but it won't connect. My ports are definitely forwarded correctly or it wouldn't connect with the IP. I'm really stumped here, any leads?