Core's biosensors use Electrocardiogram in order to measure your body's response to meditation and give you a window into your health. If you see the 'No sensor data found' message for a session, that means Core doesn't have biometric data for that meditation. This can happen for a couple reasons:
1. Your hands weren't in full contact with Core's sensors. Now, this doesn't mean you need to completely cover them, but try to keep your thumbs in contact with at least a few metal dots (these are the sensors) on each side. You'll see two lights light up between the sensors when you've made contact.
2. You have circulation issues in your hands, like Raynaud's disease for example. Core may struggle to measure your biometrics if your hands have circulation issues and are particularly cold when you meditate. If this is a problem for you, try warming your hands before your meditation. Not only will that make things a little cozier, but it should improve your data as well!
If you're still having issues after giving these a try, please reach out to us at firstname.lastname@example.org and we'll help get things back on track.