Vivomove Style Zero Intensity Minutes

Had been using a different product but switched back to the Garmin at Christmas as liked the Vivomove style - the combination of a more traditional looking watch with the movement/HR tracking of a fitness tracker.

The tracking of my resting heart rate is consistent of that of other products I have used but one thing it just doesn't seem to recognise is any intensity minutes.  At first I thought that was because the default heart rate settings were too high.  My resting heart rate averages just under 50 (am nearly 50!) and even in the middle of a high intensity workout just didn't seem to be getting above 120 (though fairly sure my previous tracker was recording higher - thought maybe I was just getting fitter!!!). 

So I adjusted the heart rate zones based on another calculation (Heart Rate Reserve).  Still nothing.  It will recognise when I go and walk the dog in the morning to get a coffee but won't also won't recognise any intensity minutes from that (but auto records the activity).  At the same time it won't recognise 4-5 hours a week of CrossFit and barbell.  Now I'm not an 'athlete' but I do put in quite an effort.

Have checked the software and it is showing as current (version 4.00).

I normally wear my watch with the watch on the inside of my wrist (have always done so). Tried wearing it on the outside - no change.  It can't be wear and tear - it's only two months old and everything else works.  And as noted above, the resting heart rate is consistent with other products I've used. Have tried wearing it more loosely as well as more tightly - again zero activity minutes.

Yes in the grand scheme of things the intensity minutes doesn't matter (ie it doesn't make me fitter) but I like to be able to at least humble brag to myself how much more I'm doing compared to the average Jo of my age.  Plus if you advertise a product as doing something then it should do it!