Offering help for the new Unicode 9.0 emoji Apple released an update for those who use the Apple Watch. This update comes with some minor bug fixes and improvements regarding performance. Shortly after, some users complained about their watches being bricked and Apple cancelled the update as of hearing the complaints.
Regarding the update being pulled the Apple iOS Watch app is showing that the latest version available is watchOS 3.1 to prevent further devices from breaking down. Those who got their Apple Watches bricked were instructed to the Apple Watch help section on their website, via a red exclamation point on their devices.
The Apple Watch support section instructed users to force restart their devices by holding the Digital Crown and the side button simultaneously. This advice however did not work thus prompting users to visit the nearest Apple Store for their device to be replaced with a new one.
There is no official statement by Apple regarding the unavailability of the new watchOS 3.1.1 but they did acknowledge that there is an issue regarding the update. The number of users that had their devices bricked by the new software update remains unknown but Apple are working on a solution to have it available as soon as possible as they released a statement saying that they are in the know regarding some Apple Watches being rendered useless after the new update.
Prompting the users to go to a retail store to have the device fixed or replaced where there is nothing that can be done in order to repair it, Apple is doing their best to come up with a favorable solution in a timely manner.
There is no apparent reason to why some Apple Watch devices shut down but the most affected device is the Apple Watch Series 2.