In my experience, auto-tagging in MusicBee is not particularly easy to use (and it only populates the most basic of tags - very disappointing). It is often quite difficult to get it to even find the proper album to start with; sometimes I have to use 5 or 6 iterations of different album names, artist names, number of tracks, etc., before it can find something close. And for multiple album sets, I have rarely seen it to find the full set at one time unless it was a CD version of an old vinyl album, where they crammed it all onto one disc. And in that last case, the details from the CD collection often do not properly match the old LPs anyway; it is best to find the tag items from the real original releases that exactly match your source if possible. Basically, you just have to do one disc at a time (and un-check any of the tracks you have included from other discs). Best to start by only selecting the tracks from one disc BEFORE starting the auto-tagging tool.