Epix Pro (Gen 2) 15.74 not automatically detecting naps

Hi there, running 15.74 and my watch is not automatically detecting naps. This afternoon, I had a 40 minutes nap and in the widget no naps today. What are exactly the conditions that the watch automatically detects a nap? I am assuming a combination of heart rate, etc, but in my case nothing got detected. Could someone please help me? I already contact Garmin via chat. Thanks.