Hello beckiboro86,
Thank you for posting to Apple Support Communities.
We understand that the Sleep feature on Apple Watch is not working as expected. We're happy to help.
For Sleep to work, the Sleep Focus need to be enabled:
"Sleep Focus: To reduce distractions, iPhone can simplify your Lock Screen and turn on Sleep Focus at your scheduled bedtime. You can also give certain people or apps permission to notify you. Learn how to customize a Focus."
Track your sleep on Apple Watch and use Sleep on iPhone - Apple Support
Once a Sleep Focus is set up, Sleep will be enabled at the set bedtime. After the events, you can see your sleep history by following the steps under, "View your sleep history".
That should help. Let us know if you have any questions.
Take care.