Most Liked From songs from Radio are unavailable when not connected to wifi

[Blanco111]

I have an ipod touch.  I noticed recently most of my Liked from Radio tracks are grayed out and can't be listened to offline.  Liked from Radio also doesn't have a green down arrow sign to the left of it as do the playlists I downloaded.  Does anyone know how I can make all the songs in the Liked from Radio to play when I'm not within wifi range?