Hollis Johnson
The problem was actually related to WiFi, Apple representatives told Business Insider during a briefing.
Basically, the Apple Watch would try to connect to WiFi before it connected to your cellular carrier, and if there was a "captive network" that throws a popup - think McDonalds or an airport WiFi network - the Apple Watch wouldn't know how to handle it, and wouldn't connect to anything as a result.
Apple said it fixed the problem in the latest version of WatchOS, the software for the Apple Watch. To update yours, go to the Apple Watch app on your iPhone, scroll down to General, and tap Software Update.
Here's the changelog:
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