Even though this is an old thread, it seems the only one in the whole 'net concerning this message.
I just saw the same message. Opened up the scope, and sure enough it has a coin cell on the main board. This is a CR 2025 (why not a 2032, come on), and it measures 0.5V without any load, so dead as a brick. And of course this is a size I don't have at hand
So when you see this message: open the scope (4 screws for the case, and 9 for the metal chassis inside, all Torx T3), and change the battery.