Health Check. 

Problem 6. 

Your Apple Watch automatically sends the health data captured by its sensors to your iPhone. This is not done by the AutoSleep app, it is done by Apple system services. AutoSleep reads the data that has been sent to the iPhone. 

AutoSleep requires this data to determine whether you are awake or asleep. 

This requires that you wear your Watch and have your passcode entered. If you do not enter the passcode, nor have a passcode set up on your Watch, then the Watch will not capture background heart rate data. 

There are a few reasons that can prevent this data from being sent to your iPhone. 
  1. Is bluetooth turned on? Some people accidentally turn it off. It’s easy to do. 
  2. Are either of the devices in flight mode?
  3. Has the Watch gone into low power mode (<= 10%)
  4. Do you have a passcode on your Watch? This is required for background heart rate data which is needed for sleep detection. 
  5. Do you have wrist detection turned on? This is also required for background heart rate data. 

If all the above are ok, then there may be a system problem. 

Here's what to do: 

1. Go into the Apple Health app, then force close it (instructions in link). Then go back into the Apple Health app, select Active Energy and wait for the data to appear.

2. If that fails, often you can solve problems like this by powering the iPhone and Watch off and on as per these links. i.e. Shut down completely and restart.