Given how fast you posted your reply, I have to wonder if you even read the posted instructions. You can make an effort to figure this out for yourself; it's not that difficult.
If you still have an active, working Google Voice account, then yes, the OBi will use that account and its Google Voice number.
Log into your Google Voice account and go to this page to confirm that it still has a number, and that you don't have some old, out-of-service forwarding phone number listed. Call the number and confirm that it still works and it can forward to say, a cell phone:
https://www.google.com/voice#phones