did you make sure its turned on in the desktop app?
that's under preferences, cloud collection. There is a toggle switch for "when you add songs from xbox music to your collection, you'll see them on each xbox music device you sign into." and "automatically add matched songs on this PC to your cloud collection"
The next troubleshooting thing would be to sign onto music.xbox.com and see if your songs are listed in the webapp. If they are, there is a problem between the cloud sync stuff and your phone. If they are not there, the problem lays between your PC and the cloud.