I have just purchased a new Macbook pro and I began to set up iTunes and download my 1000+ songs that I have purchased on iTunes. Upon going through the 'purchased' button on the iTunes store, only 580 songs have been downloaded and iTunes is now telling me there are no more songs to download, though clearly there are still 500+ more songs that I own but cannot find anywhere. Why is this and where can I find the rest of the songs? Thank you
You would need to work with Apple support to track down one specific case - but it could be that items are no longer available for re-download in your region. 500 seems like a lot of churn, but Apple doesn't guarantee you a re-download from the cloud so you might want to get your backup copies and restore them that way.
To contact support check your country here and then use the link at the bottom of the page: https://support.apple.com/en-us/HT204411