I have been trying to calibrate my watch on the treadmill but I never seem to get the option to do so. Does this watch work effectively on the treadmill?

I have been trying for the last 3 weeks to calibrate my watch on the treadmill and never seem to get the option to calibrate. This morning I did 2.5km and then a further 3km each time never getting a calibrate option and even on my first treadmill walk I never got an option to calibrate. I did get an option randomly once but at that stage I walked 5km and the max is 3km so that didnt work either. This is a highly frustrating process for me as I mainly workout on the treadmill and so I have had to go back to using my apple watch that gives me accurate readings. 

Anyone have good experience with this watch and a treadmill or is this watch not meant for the treadmill?

Just to note that I don't run on the treadmill but walk and I do have high elevations when I walk and I need a watch that can track distance with the elevations.