I think the issue they are referring to is that Lidarr’s API or interface with the MusicBrainz database has been broken for a few months now, which means it’s impossible to search or add new artists/releases to your Lidarr library.

And as far as I can tell, it’s still down. I have been unable to use Lidarr for anything since about April, except for finding releases that I had already added to my local database.