PSE2018 and iTunes Music in slideshow?

I'm a new user to PSE2018 and recently made my first slideshow.  I wanted to add music from my iTunes Library and so far have selected two different songs from two different albums - the song titles show up under the Audio portion of the Music section of the slideshow but when I click to hear either one I get a message saying "the following audio file is either missing or corrupted" - but yet they each play perfectly fine when I'm in the iTunes Library.  What am I doing wrong please?