To have Facebook as a sales channel, your product must require shipping. Since my products are digital I set the shipping weight to 0 lbs and made my shipping rates 1 lbs and up. I also changed the "shipping address" to "customer address" in the shipping section of the checkout cart language under settings. Here is a forum entry which gives a little perspective on the issue from another Shopify merchant.
Once I made the above changes, every product from Big Band Chart Store that had a shipping requirement added (whether it was a digital product or not) very quickly populated my Facebook page at Bill Fulton Music. Te products are also available through the Facebook checkout further streamlining the order process.