Whoops! Your keyboard is all out of juice. To get it working again, put it under strong light and leave it exposed to strong light when you're not using it. It may take a few days to recover and weeks to get back to a full charge.

Want to make sure it's getting enough light? Use the Check Light hot key on the keyboard and check the lux gauge. It should be 300 lux or more to get your keyboard back on track.