Mac Mini always ' Always Allow ' Incoming Connections

Hi ,
Been annoying me for months but only really become a problem as I'm trying to up my 2012 Mac Mini's (2.6ghz/2tb)
ease of use for everyone . As it is used as a Media Server I have set it to automatically log in at power on and just launch
3-4 of the most used Music/Movies programs including Plex Media Server .

Everything works perfectly except only Plex asks on every launch for permission to allow incoming connections despite being listed as a log-in item and being set in the Firewall Exceptions to ' Allow Incoming Connections' .

I'm baffled ,

Any ideas ?

Thx

~M~