It seems that you are having some issues when trying to set up your Slingbox PRO-HD with the Asus RT N16 router.
Unfortunately, we do not have a tutorial for this specific router model, however, the following third-party link will allow you to get some steps to follow. Hopefully, it will help you:
If you are able to complete the Setup Assistant for Internet Viewing, I recommend you check the following link. It will allow you to get the step-by-step instructions in order to know how to set up your Slingbox PRO-HD for Internet Viewing with a two-router network:
If the issue persists, I encourage you to contact your router provider in order to know if there's any kind of restriction (or firewall) that might be preventing you from getting this connection. Let us know how it works for you and post your results.