Thanks for using our Answers Forum. I understand that you purchased a second Slingbox SOLO and would like to add it to your account. That is not a problem at all. When you first plug in the Slingbox, you might want to do a "hard reset", hold in the reset button on the back of the Slingbox for at least 30 seconds. This will set the Slingbox back to factory settings. I also have an article that should provide you with any further information that you may need.
Hope this helps.
Sling Moderation Team