Currently Being ModeratedAug 30, 2012 8:49 PM (in response to Oscar.Zapatau)
You may need to authorize your computer for the Apple ID(s) used to purchase your music (and apps) in iTunes>Store>Authorize this computer. Also, if you are trying to manually manage your music with drag and drop make sure that you have checked "manually manage music..." on the Summary tab of your iTunes sync settings. Finally, you may need to log into your Apple ID in the iTunes>Store menu.
Currently Being ModeratedNov 30, 2012 10:15 AM (in response to Oscar.Zapatau)
I just had this problem. I went into my Itunes settings on my phone and turned off Itunes Match. Solved the problem.
Currently Being ModeratedSep 30, 2013 8:25 AM (in response to Oscar.Zapatau)
I just had to go back in and reselect the box "Manually manage my music and videos" under the summary tab like Randers was saying and BOOM problem solved.