One thing that I’ve learned about troubleshooting Back to My Mac is that you have to jump through all of the hoops that Apple lists in their support article “Set up and use Back to My Mac” (http://support.apple.com/kb/ht4907). Recently, my work Mac wouldn’t show under “Shared” in the Finder sidebar. The problem was solved by this instruction: “3. Open a Finder window, and look for the Shared section in the sidebar. If you don’t see any shared computers or base stations, place the pointer over the word Shared and click Show.”