Adding music to a video with iMovie

Hello all,

In the past, not too far, using my playlists in iTunes and even in Music, I was able to show the musics in iMovie and add to a video.

Now I am not being able to do that as iMovie says the songs are "protected". I never did anything illegal when adding music to my video clips and I want to continue to do that.

Does anybody knows how can I do such a thing ?

Thanks Paulo