Some users have experienced an issue which results in a red exclamation mark being displayed on the screen following installation of the new firmware. The device instructs users to visit www.apple.com/help/watch where a force restart is suggested. Unfortunately, that doesn't work and users are only left with the option to contact Apple for assistance.
You can watch a tutorial on how to force restart your Apple Watch here. Most of the units affected appear to be Series 2 models.
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