Playlist won't show when I want to add songs to it?

I have recently made three playlists (using the create playlist option you can do on windows)

All three show up fine under playlists, but when I want to add certain songs, two of the playlists show up in the options but not the third one.

I am using Sansa Fuze+ 16GB black. Anything I can do to fix this?

The two playlists are Edits and Medleys. The third one is named ‘Idolmaster’ and it didn’t show up. then I tried “IDOLM@STER” but it also didn’t work. I’m telling the names to let you know that I’m not using any special characters that could possibly cause errors.