ive had pretty much the same setup for about a year. mac mini with a hard drive plugged in runs the server, and then i have a choice of ways to connect to it. the mini is plugged into the tv, but im more likely to use either my smart tv plex app or my ps 4 app to connect for 2 reasons, they look better plus my 2009 mini sometimes loses sound from its optical output (known problem). plus i connect from my iPad.
i do have a smart dns unlocator.com which ive used for a long time.
all of a sudden for the last 3 days, any attempt to connect from any device says it cant connect to the server. however the mini is working fine, its connected to the wifi, and using safari i can play anything from it using plex on that.
ive restarted everything to no avail.