trouble with iTunes Match and not being able to get higher quality files downloaded

trouble with iTunes Match and not being able to get higher quality files downloaded

I’m not doing something right, I turned on iTunes Match so I could get 256 kbps files of my older lower quality music. It shows in ITunes that many of my songs have been matched. I then turned on automatic downloads for music but none of my existing files are being overwritten with the higher quality version from the icloud. What am I doing wrong?