https://techcrunch.com/2018/11/05/apple-watchos-update-bricked-watch/

Apple has rolled out watchOS 5.1.1, less than a week after the company pulled its immediate predecessor, watchOS 5.1, following reports that the software was bricking some Apple Watches.

The update also includes bug fixes for the Walkie-Talkie app and an additional issue where some Activity rewards were not displayed.