Most issues can be resolved by resetting the watch, and there are a few ways to do so.
If the screen is working and you can navigate the menus, swipe from right to left until you get to "System" (it's the last menu item).
From this menu, scroll down until you get to "Factory Reset" and tap this menu item.
You can then confirm the reset. You will not lose any information, but it will put the watch back in the original settings.
You can also simply shut down the watch, and turn it back on. To do so, go to the "System" menu and tap "Shut Down"
If this does not resolve the issue, please contact us at email@example.com.