Thanks for using the forums. Sorry to hear you are having troubles using your iPhone application for the Slingbox.
Once your Slingbox is set up and ready to view, you should be able to view wherever you are in the world. You wouldn't need to be on the same network for the iPhone application to recongnize your Slingbox. When you log in, are you using the same email and password that you use to log in to your computer? You will want to make sure it is the same. If it is still saying there are no Slingboxes in the account, you will want to uninstall and reinstall the application and then log in again using the same email and password as the computer and then will be able to view your Slingbox. Please see the article below for more help uninstalling and reinstalling the application.
Hope this helps,
The Sling Moderation Team