1.Check your iPhone Health app to see if any sleep Data exist. 

Health > Show All Health Data > Sleep

If there is no data available, Set up sleep tracking and wear your Apple Watch while sleeping. Updated data will be available after waking up. Note that Sleep data might not be available immediately after waking up.

2.Confirm that you have allowed Sleep Details to read your sleep data.

Open Settings app on your Apple Watch > Health > Apps > Sleep Details
Turn All Categories On

3.Open Sleep app on your Apple Watch to see if sleep tracking is set correctly

contact@sleepdetails.com