Songs do not have plus to the left and will not play on iphone

[cup4sale]

I have noticed that several songs in spotify lack the the "+" sign to the left.  I can drag them into my playlist on my computer and play them there, but on my iphone the song name appears and then is skipped (i.e. it won't play).  Even if I specifially look up that song on my phone and select it, it will not play.  I posted of some of the songs in question.  Anyone know what this is about?  

[Joe]

Probably better to post in the iOS section.