Wrist Temperature not showing on Health app

Just to make sure, you are wearing your watch at night?

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Here's what you need

• An Apple Watch Series 8 or later, or any model of Apple Watch Ultra.
• Sleep must be set up with Track Sleep with Apple Watch enabled.
• Sleep Focus must be enabled for at least 4 hours a night for about 5 nights.

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copied from: Track your nightly wrist temperature changes with Apple Watch - Apple Support

I had to wait another 5 nights, after I unpaired the watch and paired it again.

Although nothing else changed, same watch, same iPhone.

Maybe you should wait a couple of more nights, according to the message, there is still some data missing.

You have already force restarted your watch and iPhone after the latest updates?

Force restart iPhone - Apple Support

Restart Apple Watch - Apple Support

Did you notice my reply above?

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Maybe you should wait a couple of more nights, according to the message, there is still some data missing.

You have already force restarted your watch and iPhone after the latest updates?

Force restart iPhone - Apple Support

Restart Apple Watch - Apple Support

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So, did you force restart your devices already after the latest updates?

If this does not work, erasing and paring the watch again would be the next step, to rule out a software issue.

Unpair and erase your Apple Watch - Apple Support

This will also reset your temperature data and you will have to collect data again for additional 5 nights during your sleep with an active sleep schedule.

Has the wrist temperature been working in the previous watchOS 10 version?

And, while you are checking the settings, make sure this feature has not been disabled accidentally: