If the server is "invisible" the mostly likely problem is your PF configuration. If PF is configured, look to your rule set.
When I was having trouble when first using minidlna, I started the daemon manually with -d, and logged the output.
Code:
Usage:
minidlnad [-d] [-v] [-f config_file] [-p port]
[-i network_interface] [-u uid_to_run_as]
[-t notify_interval] [-P pid_filename]
[-s serial] [-m model_number]
[-w url] [-r] [-R] [-L] [-V] [-h]
Notes:
Notify interval is in seconds. Default is 895 seconds.
Default pid file is /var/run/minidlna/minidlna.pid.
With -d minidlna will run in debug mode (not daemonize).
-w sets the presentation url. Default is http address on port 80
-v enables verbose output
-h displays this text
-r forces a rescan
-R forces a rebuild
-L do not create playlists
-V print the version number