Iwatch not recognizing exercise minutes

i use the Apple Watch”Workout” for “outdoor walk.” Everything about the data within that app seems to work fine. It registers minutes, distance, etc.

However, it usually does not register over into the green circle activity as minutes of exercise. If I walk and hour, I might get five or 15 minutes. More likely, I will get zero unless if I pause The walk and resume it then it will start to count the minutes in the green circle again for a moment or two.