Soundbar turns red, and becomes unusable

Hi Everybody,

I'm new on this forum & FCP, but having a pretty big problem so I need some help from above!

When I want to add music to my video's the music bar/sound bar and the file in the libary colours red and doesnt play a sound. I have used the music in multiple video's before, but suddenly they start to fail.

I always drag the music from my itunes into the video clip. This is how I've always done it. It always works, but now one for one the music is failing (some work, some don't).

This sometimes means that I finally found the perfect sound, and then I need to search for a news song and download new music. All of my most used songs don't work anymore, so when I want to export an old file I first have to search for new song. (importing the song again doesn't work!)

I hope I explained my problem, a screenshot in the attachment!

Does somebody know how I can keep using my music?