Apple Watch Series 5 Cellular unable to set up cellular data due to watchOS requirement

Apple Watch Series 5 Cellular – unable to set up cellular data

Hi everyone,

I have an Apple Watch Series 5 Cellular that I purchased around 2019/2020, at a time when Apple Watch Cellular was not officially supported by carriers in Croatia.

Cellular service is now available in Croatia through Hrvatski Telekom (HT), including their OneNumber service for Apple Watch, so I would like to activate the cellular functionality on my existing Series 5.

My current setup is:

• Apple Watch Series 5 Cellular
• watchOS 10.6.2 (latest version available for Series 5)
• iPhone 16 Pro
• iOS 27

The problem is that in the Watch app, under Mobile Data/Cellular, the “Set Up Cellular” option is greyed out. The app says that I need to update the Apple Watch software before I can set up cellular data.

However, Series 5 cannot be updated to watchOS 11 or later. This leaves me in a loop: the Watch app requires a newer watchOS version, but no newer version is available for my Apple Watch.

Has anyone encountered this issue with a Series 5 Cellular?

More specifically:

• Is Series 5 Cellular still technically capable of being activated with a carrier on its latest supported watchOS version?
• Is the greyed-out “Set Up Cellular” option a known limitation/bug with newer versions of iOS and the Watch app?
• Is there any workaround that allows the carrier to activate/provision the Apple Watch without going through the blocked “Set Up Cellular” process in the Watch app?

I would especially appreciate input from anyone who has successfully activated a Series 5 Cellular recently, particularly with a newer iPhone and a carrier that supports Apple Watch cellular service.

Thanks!