The unit that allows you to connect to the Slingbox and then get disconnected, it sounds like the Internet Viewing was not setup correctly.
If you go to setup.slingbox.com on a computer that is on the same router as the Slingbox and click on "Get Started". Once there click on "Set Up Internet Viewing" icon. An image below shows you what to select:
If the test fails or indicated that the setup is almost complete, you will have to manually port forward your router. The following website can help you locate your router information and will give you information on how to port forward your router for your Slingbox:
On to the Slingbox that is no longer working. Try trying the steps in this article below:
Hope this helps!!!
Sling Media Moderation Team