At least seems like it's working...more?
It's still not right, but I'm pretty tired and at this point it could just be me. It is, right now, displaying a 'searching for songs' bar that it wasn't before, though it still doesn't seem to pick up any songs.
I also had an attempt that came close, where I... don't know what I did exactly. I wasn't picking up the song, so I tried adding the one song directly into my library, and then trying to switch the data to it. I ended up with two copies of the song, and neither would make any noise when played.

Anyways, I'm still not actually picking up any songs with a search, but... I'll give it a more thorough try tomorrow. Thanks though!
EDIT: Huh. Apparently it may have been because it was an .m4p? More on that later...