Store Song Removed
If you're seeing this page it means you picked a song for which the "ID" no longer refers to a song in the store.
This can happen when the store changes the "ID" of a song, or if licensing was revoked for that song by the publisher.
You should first make sure you have the latest copy of the store. To do that, Context Click on the store name and pick "Reload Music Store". After it reloads, search for your song again, if you find it, then clicking the "buy now" button will work.