Won’t track sleep

No, a third party app is not required.

You need to setup a sleep schedule in the Health app on your iPhone first though.

Here is a link to a helpful article:

Track your sleep on Apple Watch and use Sleep on iPhone - Apple Support

Let us know if you need anything else ;-)

Check this setting for me please...

From within the Watch app on your phone, go into Sleep. Make sure that the toggle for "Track Sleep with Apple Watch" is green.

If you can't find "Sleep" listed, then that's another setting that we need to check, but it's found in the Health app on your phone. Open Health, click Browse (lower right corner), click Sleep, scroll down to and click on Full Schedule & Options, look for "Track Time in Bed with iPhone", the toggle needs to be green.

Let me know what you find out. We'll get this going ;-)

Nice! B-)