Edge 810 sync power data to Fenix 7

I’ve been using a Garmin 810 for a few years now. I recently purchased a Fenix 7 watch. Both devices sync properly to Garmin Connect on my phone. But my power data from the 810 will not upload to my watch to give me Cycling Ability or VO2 Max. 
Why is this? I’m told that I need to record my training rides on both devices. Why does Connect not auto upload power data to my watch? It will upload rides and miles.