I see someone else was having this problem but the discussion is now locked.
Just recently, recording an outdoor walk on my fēnix 7S, the watch does not display either the distance or the pace, but shows the map and shows I'm connected to "All systems".
When I save the walk, the data on the Connect App and Web shows all the time data and the map of the walk, but no distance.
Once that is sync'd to Stava, the distance is shown (along with the map), so the distance is definitely being recorded.
Well, I do not know what causes it, but the FIT file indeed shows completely missing distance data, although the GPS data and GPS speed are included. I suspected it happened due to incorrectly trying to use some of your external sensors, but that was not the case. For some reason there is no device assigned for recording the distance and speed (though the speed was recorded anyway, despite it). Below, there is the device assignment in your FIT file, and the next is the assignment in my walk activity - the distance is alternatively measured either by the GPS (ID 5 in my file, in yours GPS would have ID 2) or by the accelerometer (ID 2 in my case, and ID 3 in yours), depending on the quality of the GPS signal.
I have no idea why none of them was used in your activity, because both the accelerometer and GPS were available. I can only speculate that the calibration for the accelerometer was missing, and GPS signal was not good enough. In you place, I would try several steps:
