I had to manually charge the battery outside of the watch as it had entered “over-discharged protection” (reading 0 volts) and the watch doesn’t appear to have the power to kick the battery back out of that mode. It only needed “charging” manually for a minute or so before it had enough power to run in the watch and charge that way. Did it on a breadboard with some solid core wire hooking up the positive (left wide gold pin) and ground (silver casing). I know they come sealed, but would be nice if the batteries were tested/charged enough before being sent out. I wouldn’t expect many people to be able/willing to manually charge a battery with the size of the connector, and also because it carries some risk!

Symptoms of this were the green charging snake appearing for less than a second, and then the watch not responding when pressing the button. It should wake the screen back up if the battery is okay/charging.