Local files not showing up in Spotify

[rjp1111]

My local mp3 format files are not showing up in Spotify. They show up in my PC music library and in Windows Media Player, and those are both turned on as local file sources in Spotify. I tried uninstalling Spotify from all my devices, then I reinstalled on just one PC - still no local files. These are songs that are not in the Spotify catalog (which is why I want to use local files). Any suggestions on how to get local files to show up?