How can I download GarageBand loops?

I'm a pretty big GarageBand user. I have a lot of grayed-out loops and whenever i click on them to download them, i get a pop-up saying: "The Software Instrument or Apple Loop selected is not currently installed on your computer. Would you like to install the complete set of GarageBand instruments and loops?" Then I get two options. Download Now, and Download Later. Download later does not do anything that it says it will do. If I open Software Updates, there is no box telling me that I have loops to install. If I chose Download Now, the App Store pops up, and takes me to the Updates tab. There is nothing in it except for a message that says "You have no updates". 😢

Please help me download these loops!

-- Thanks in advance,

Andrew