Back to My Mac Connection Problems
Back to My Mac can be quite difficult to get up and running correctly. If the router that provides incoming access to a remote computer doesn't have a publicly reachable IP address, then you can't use Back to My Mac to access computers on that router's network.
If you know or believe that you have a publicly reachable IP address, then follow this troubleshooting advice:
Start with Configure Your Router or Gateway (p. 66). This appendix describes how to set up your router to allow incoming access to computers on your network. If you haven't configured your router before trying to use Back to My Mac, make sure that it's set up as needed.
Do the local computer and the remote computer have either the same Computer Name ...