If you recorded a session with your iPhone or iPad only
This is probably due to the fact that Pillow does not have access to your motion data. In this case please verify that Pillow has sufficient permissions following these steps:
Open the "Settings" app on your iPhone or iPad.
Go to "Privacy & Security" > "Motion & Fitness".
Make sure “Fitness Tracking” is enabled and Pillow is also enabled in the respective list of apps.
If you recorded a session with your Apple Watch
The most probable cause for this issue is that Pillow couldn’t find any data to perform sleep analysis.
Please make sure Pillow has all the required permissions:
1. Open the "Apple Health" app on your iPhone. (It has a white icon with a red heart.)
2. Tap on your profile icon on the top right of the screen.
3. Tap on the "Apps" > Find and tap on Pillow.
4. Turn OFF all the available switches.
5. Restart your iPhone and Apple Watch.
6. Open the "Apple Health" app on your iPhone > Tap on the profile icon > Select "Apps" > Select Pillow > Turn ON all switches.
Make sure you wear the Apple Watch that is currently active:
If you have paired more than one Apple Watch device, please make sure that the Apple Watch that you wear during sleep is the one that is currently active.