It is my understanding that only one person can watch the Slingbox at a time. And, I further believe that if the Administrative User is watching the Slingbox, then none of the guest users will able to watch at the same time. When I no longer wish to watch my SB as the Administrative User, I always "disconnect" from the SB in my Sling Player standalone software or in my web browser plug-in before exiting the software or web browser, in order to insure that I (or my guests) will be able to watch later without getting blocked out.
Don't know if this action on my part is essential, but it can't hurt anything.
What I'm getting from your post, is that your Slingbox is not connecting from a remote location.
In this case as a first step, I would recommend to make sure you created the guest account properly, you can check the following link about it.
Besides that, make sure that the Slingbox Internet Viewing is properly configured and also, you can provide more information about the issue that you're having, such as error messages, network layouts etc. That way, you will be able to receive a proper response.