It's likely a network configuration issue on your end, I'm sure we can get to the bottom of it. Presuming you have a computer of some sort on your network (and that computer can ping your Arduino), we can try to verify your connection to arduino.mydevices.com
If it is running OS X or Linux, you can run
telnet arduino.mydevices.com 8442
on your command line.
If things are working, it will disconnect you right away, but you'll get a message like "Connected to arduino.mydevices.com" first.
If you're running Windows, you can download PuTTY: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html to make the same test. You'd be looking for these settings:
Once you click 'Open' there, if you get a popup with 'Connection closed by remote host', then your computer is able to communicate with arduino.mydevices.com on port 8442. If you get a blank black window and no popup message, you're blocked for some local reason that we can continue to help you figure out.