'Check lens. Pictures can only be taken when a lens is attached' - Warning Message Appears

With a Nikon 1-Series camera (such as the J2), you will need to make sure the camera is in 'Manual' exposure or shooting mode and the focus selection is also set to manual. When in any other mode the camera tries to take control of the lens which is not possible as the adapter does not have any contact with the camera circuitry, so you get the lens check warning as the camera does not think there is a lens attached.