Today, Apple released watchOS 4.0.1, an update that is designed to fix a Wi-Fi issue that some Apple Watch Series 3 models with LTE cellular capabilities experienced. The issue, which had caused some early Series 3 reviewers to pan the device when they ran into the problem, caused the Watch to connect to an inaccessible but familiar Wi-Fi network instead of to an LTE network.
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As noted in the update notes seen above, “watchOS 4.0.2 fixes issues that, in rare cases, were causing Apple Watch to join unauthenticated (captive) Wi-Fi networks, such as those found in public places like coffee shops and hotels, which direct the user to a webpage before the network can be accessed.”
To install the update, go to the Watch app on your iPhone, go to General > Software Update. Place your Apple Watch Series 3 on its charger (it must have at least 50 percent of a charge to even begin downloading the update), and make sure it is connected to Wi-Fi.