Yesterday Apple focused on announcing a series of device updates, including a new MacBook Air with Retina Display, a long-overdue Mac mini-update and new 11-inch and 12.9-inch versions of the iPad Pro. But these are software updates that we are talking about today, and especially the botched version of watchOS 5.1 for Apple's smartwatches.
Something has gone awry with watchOS 5.1, so trying to update an Apple Watch Series 4 results in a quarry. As reported by 9to5Mac, the issue seems to be limited to Series 4 devices, but it is serious enough that Apple pulled out the update. If you downloaded the watch, you should not update the watch now because you may have a dead watch.
No explanation was given by Apple as to what happened, but you know watchOS 5.1
WatchOS 5.0 was released on September 17 and introduced a number of improvements to Siri and notifications. They also added walkie-talkie and podcast apps, new types of training, and are usually smarter about identifying your activity. Yesterday's update to 5.1 was supposed to introduce the 70+ new Emoji, which is also included in iOS 12.1, but that will definitely have to wait until Apple finds out what went wrong.