[Roy Dennis]

First of, if you enter the book id of one of the missing songs into the search box does it find it and does it play if you add it to the playlist ?

If it does right click on it in the playlist and select "Edit Song", when that dialog opens check that the info entered into the artist and title fields is correct and also do you have any of the boxes at the bottom ticked like Duet, Hide in songbook or multiplex ?
It would be helpful if you could attach a screenshot of this page.

Now open the Songbook Dialog. what range of songs do you have selected ?
Entire song book or one of the other options, also do you have the box ticked for exclude checked items ?
If so which boxes do you have selected to exclude in the right hand panel ?
Again it would be helpful if you could attach a screen shot of this dialog as well.