Garmin not tracking miles

My Garmin Vivoactive 5 does not track the miles correctly when I am walking.  The treadmill will say 3.55 and I have the Under Armour Hovr shoes that track the miles to Map My Fitness and the miles will be 3.60, but my Garmin say 1.86.  I don't hold on, my arm swings, so it's not that there isn't movement. The steps track just fine, but the miles do not.  I have tried just selecting Walk, then Walk Indoors, and then Walk Treadmill and they all do this.  I have the GPS set to All Systems on Walk.  I am just not sure what the problem is.  

Is there something else that I need to do to my Garmin to get it to track the miles accurately?

Thank you..