m4a files not importing to iTunes!

So, I've done this a million times before: I have an m4a file (a voicememo from my iPhone), I drag it into iTunes, and then I convert it to an mp3.

NOW.... For some reason, SOME of my m4a files simply don't import into iTunes. I drag them there, and they don't go.

The file names are not long. Nothing's weird about the file names.

I've tried everything, and I've been Googling forums for an hour. PLEASE help me!

yep! i tried "Add To Library"
no error message; files just don't add


thanks!

Well, I got it working. It was something about the files themselves. When I downloaded them using iExplorer instead of iTunes synch, the files work as expected. Thank you for your helpfulness anyway!