Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Are you trying to load music from iTunes Match on a cell connection with the "Download Using Cellular Data" (or whatever it's called) option turned off?

I am using Wi-Fi and trying to listen to songs already downloaded to my phone.
 
You have to go into iTunes on your iphone and agree to the updated terms of service. Same happened to my friends phone. I turned iTunes Match off and then back on, that triggered the service agreement pop-up for me. But you could probably just try to purchase a song to get the terms agreement. After you have accepted the new terms iTunes Match should work again.

Wired bug. Hope this helps.
 
Yeah, it happened to me last week as well. Turning off and on iTunes Match won't solve the problem. Instead of playing the song, click on the Clould icon instead, and it should prompt you to accept the new agreement. Once you hit agree, it'll work.
 
Gave that a go, and what I've found is any song I've downloaded to me phone doesn't work but any song which is still in iCloud so to speak does. Very odd.
 
All songs which haven't been downloaded work. Any song which has been downloaded just skips.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.