There is a number of reasons you may see this message.
The most likely cause is that Library Player can not find the folders where audio tracks are stored.
You may wish to check the following:
- If you store audio files over a network, the network connection may be down.
- If you recently moved, deleted or renamed files/folders check the settings to ensure Library Player is still looking in the correct folders.
- A track added to the Playlist or Fast Jingles may no longer be available (e.g. a server may be down so an audio file is not accessible).