Exactly. 99% of these issues are not naming the files as Jellyfin needs, which I understand can be annoying if you have a large number of files to move to it. And having the right access permissions for files, if you are on Linux.
Filebot is nice for that, it is what I used when I first got into Plex and realized the reason I had so many problems is because of the way I named files. This was before I even knew Sonarr and Radarr existed, now you can get them to do it.
