Not all solo titles in SmartMusic contain on-screen notation. The music publishers in these cases expect soloists to have already purchased the music separately and read from their sheet music while SmartMusic is accompanying them.
If you are browsing for new material that you can read directly from SmartMusic, watch the column on the far right of your search results labeled "On Screen." If there is a check mark in this column, you will be able to read the music on screen in SmartMusic.
You can find sheet music available for purchase for most titles within SmartMusic at J. W. Pepper's website.