"automatic sdf downloading is disabled or failed"
However , makemkv continued to process the disc, listed the titles, and even highlighted the probably main title as "FPL_MAINFEATURE".
I checked "Preferences->General" and downloading updates from the web server is enabled. What is the web server hostname? I have pi-hole and pfBlockerNG running to filter DNS requests. I can check their logs to see if they blocked it. I found requests for makemkv.com which were allowed, so we are good for that domain

Is it a serious problem that I should look at fixing? I don't know what SDF is so some context would be helpful.
Software info:
MakeMKV: 1.12.3
OS : MacOS 10.13.6
Java: 1.8.101
Moderator edit:
Closing this topic because it has a shorter replacement. For detailed help on this, please read the Fixing Volume Key thread.