I use a Polar H10 chest strap sensor and from the time it's connected to the time it's removed (unpaired), the watch and/or the Connect app will not register Intensity Minutes. And if I use the watch for an activity with the external sensor, it still won't register the Intensity Minutes.
This makes Intensity Minutes useless and kills my plan to use them as some sort of goal.
I'm new to Garmin. This is a bug report. Happy to add more info if it can help. Thanks.