It seems that you are no longer able to get the connection to your Slingbox while running the SPM application on your iPhone.
This issue might be related to any recent restriction applied by your ISP. In all case, we recommend you to set the Direct Connection on your computer as a second connection option. Then, you will be able to pull it up when using the Direct Connection on your iPhone.
The following link will provide you with the steps to follow in order to enable the Direct Connection option.