Why are certain songs listed as unavailable?

I recently uploaded my iTunes library to iTunes Match so that I could stream over my phone. After uploading, I notice where certain songs on my phone come up with the message "ITEM NOT AVAILABLE...This Item Can't Be Played". I had originally thought that the song may not have been uploaded to match which is why it would be marked as unavailable, but upon further review noticed that all of these "unavailable" songs had indeed been uploaded and were just unavailable for some reason. Any answers?

I also have a number of songs that were not uploaded and have a cloud with a slash through it where it says "This item is not eligible for the iCloud Music Library." why is this? and is there a work around?