I saw a question on DC's 955 post.
I decided to Try it and I deleted the Run Dynamics Data Page from Run Activity.
For some reason you cannot see it in the selection list to re add it after having deleted it as a Data Screen.
I thought maybe I needed the HRM attached to activate it so I tried that to no effect.
I tried both on the watch and the app as I've seen a few instances where som action on the watch isn't possible on the App.
Did a long power reset , not working after that either,