iPhone lose sync data from Apple Watch.

Hello gan192,

To help better assist you, can you confirm if sleep data from Apple Watch isn't appearing in the sleep history on your iPhone?

1. For the process to view your sleep history on your iPhone, please check out this link, which explains how to do that: Track your sleep on Apple Watch and use Sleep on iPhone

View your sleep history

Based on your iPhone usage at night, Sleep on iPhone tracks and charts your Time In Bed. To receive sleep data from Apple Watch, sleep tracking must be enabled for at least 4 hours each night. 

To view your sleep history, open the Health app on your iPhone, tap Browse at bottom of the screen, then tap Sleep. If you have Sleep saved as a favorite, you can access it from the Summary page in the Health app.

The bar graph by default is set to D for daily. Tap W at the top of the chart to view your sleep history for the past week, M for the past month, or 6M for the past 6 months. Tap Show More Sleep Data and select a category to review additional sleep details.

• Stages: View the time and percentage you spent Awake or in REM, Core, or Deep sleep.

• Amounts: View your Sleep Duration details such as Average Time in Bed and Average Time Asleep.

• Comparisons: View your Heart Rate and Respiratory Rate in relation to your time spent asleep. If you have Apple Watch Series 8 or Apple Watch Ultra, you can also compare changes in your nightly wrist temperature data.

2. If you need further assistance with Sleep, please contact Apple Support. You might be able to reach them here: Contact Apple Support

Thanks!

Hello gan192,

Please use the previous provided resource to contact Health Support for further assistance.

Take care.