"Network discovery" is set to "Disable" after restarting service
provided an Auto-IPTV- Network where "Network discovery" is set to "New muxes and changed muxes" and you run "sudo service tvheadend restart", then "Network discovery" is automatically set to "disable".
So you have then manually to change this setting again. It would be more cool, if the previous setting would persist even after restarting the Service. I´m using Raspbian-stretch.
have a great day :-)