It seems that you are having some issues in order to set up your Slingbox SOLO for Internet Viewing with your home network.
Since you are using the Airport Express and Airport Extreme to set up your Slingbox for Internet Viewing, first you need to make sure that the connections are properly made. I recommend you to verify the connection among the Airport devices (hard-wired or wireless connection) and make sure to adjust the settings in a proper way. The following links (including a third-party link) will provide you with the steps to follow in order to set up your Slingbox for Internet Viewing:
Hope this helps!