The Polaroid 600 OneStep series uses Polaroid's 600 Platinum film. This type of film cartridge contains its own battery. If your Polaroid 600 OneStep will not power on, the chances are good that the film cartridge's battery is dead. Unfortunately, this renders the film cartridge useless; it requires replacement. Once you replace it with a new film cartridge, the camera should power back on.
Open the flash lid to expose the lens. Press the film-door release button on the bottom side of the Polaroid. The door opens.
Remove the old film cartridge. Because the battery is dead, dispose of the old film cartridge.
Insert the new film cartridge into the slot. Raise the film cover. The Polaroid will eject the film-cartridge sheet. Pull it out and discard it. Close the flash lid.