Why isn't my iTunes library showing up on the cloud
Why isn't my iTunes library showing up on the cloud?
Why isn't my iTunes library showing up on the cloud?
How are you trying to access your Music in the cloud?
Have you signed up for iTunes match and let it upload your library? Are you signed in, when you are trying to download from the cloud?
See this help document for common troubles with iTunes Match: http://support.apple.com/kb/TS4054