ITunes Song Sync Not Working

So I got my shiny new iPhone 6 and -yaaaay ! - for the first time I can sync my entire music collection (60GB). Not wanting to blow my monthly internet limit downloading from the could, I switched on ITunes Match on both laptop and iPhone and proceeded to sync over USB.

When the sync process finishes, the vast majority of the songs on my iphone show a "downloading" symbol next to them - a red square inside a red circle - and nothing happens. Any ideas ?