https://techcrunch.com/2017/09/20/apple-is-working-on-a-fix-for-watch-series-3-lte-issues/

The new Apple Watch is mostly an iterative update over its predecessor, but for one major feature: LTE. The addition of cellular connectivity has been touted as everything from “nice” to “game changing,” but reviewers appear to have early issues in testing. I didn’t run into any in my own testing, but the Verge reported some big hiccups connecting to the cellular network on the device.

An Apple spokeswoman confirmed the problem with TechCrunch, stating, “We have discovered that when Apple Watch Series 3 joins unauthenticated Wi-Fi networks without connectivity, it may at times prevent the watch from using cellular. We are investigating a fix for a future software release.”