New Apple Watch Series 3 owners who are trying to turn on the device’s cellular connectivity are finding they can’t, The Wall Street Journal is reporting. Apple confirmed to the Journal in a statement that the cellular connection “has been suspended.” China Unicom, a Chinese carrier, said in a statement on its website that the cellular connectivity was only offered on a trial basis.

Apple released the Apple Watch Series 3 last month. The device has the same design as its predecessor, the Series 2, but is the first smartwatch from the tech giant to use LTE wireless connectivity. The feature allows users to connect the Apple Watch to a carrier network and do everything from place calls to send data over the network without needing an iPhone. The feature effectively turns the Apple Watch into an iPhone sitting on the user’s wrist.

According to the Journal, those who purchased the Apple (AAPL) Watch Series 3 in China when the device went on sale on September 22 were able to get the cellular function working. After September 28, however, the feature was turned off to all new subscribers. Those who added the feature before the cutoff are still able to connect.

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It’s unclear why the ban has been instituted, and the Chinese government hasn’t commented on it. However, the Journal cited industry analysts, who said the ban was likely due to the Chinese government not having an easy way to track users. China has some of the strictest regulations in the world for monitoring mobile users, and Apple Watch Series 3 might be presenting problems the government hasn’t yet addressed.

At the heart of the government’s problem is a technology Apple uses in the Series 3 called an eSIM. The component allows the Apple Watch to connect to carrier networks and send and receive data over those connections. While the eSIM is similar to a standard SIM inside a smartphone, it doesn’t readily identify the user, making it troubling for a government like China, which tracks all of its users.

Looking ahead, it’s unclear what might come of the ban. Apple Watch Series 3 is still available in China, but a ban on its critical feature might prove to a problem for Apple and its sales there.

Apple did not immediately respond to a Fortune request for comment on the report.