Please check if you gave all the needed permission to access your Health data. NapBot uses the Health app to access your calories, heart rate, motion to learn, and understand your sleep patterns. If you are not sure about permissions, please reboot both your iPhone and Apple Watch devices, open Health app -> Your Profile -> Apps -> NapBot and turn on all the permissions.
Another thing you have to do is keeping app alive in background. Please don't kill or close the app via app switcher on your iPhone.