This can happen when the watch tries to join a Wi-Fi network the user has previously logged in to using another Apple device, such as an iPhone or a computer. But Apple has acknowledged that this centrepiece feature isn't working exactly as intended.
The problem comes to light after demand for the Apple Watch Series 3 with LTE appears to have far surpassed analyst expectations, and now has shipping delays of up to a month. Unlike previous versions of the watch, it has cellular network connectivity built in.
In a statement to the Verge, Apple said: "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".
Apart from connection issues, some reviewers were disappointed with the drain on the watch's battery while making calls.
The company is "investigating a fix for a future software release", Apple spokeswoman Amy Bessette said.
This resulted in an occasional inability to place or receive phone calls and text messages, or access Siri. Cellular connectivity is a major selling point for the Apple Watch Series 3's, and if that doesn't work as promised, users could avoid buying the device when it goes on sale Friday.
Apple replaced Lauren Goode's review unit, but she had problems with the second Apple Watch too. Apple chief executive Tim Cook apologised for the rocky Maps launch, a stark contrast to his predecessor, Steve Jobs, who once told people having trouble with their iPhone's connectivity to hold their phones a different way.