Intensity Minutes stopped counting.

Take a look at your resting and maximum heart rate settings, as they affect what is considered an "intensity method". If you know these numbers, enter them directly rather than using autodetect.

Because auto detect doesn't work right on this $700 fitness tracker that's been around for 9mo the market. And FYI hasn't worked right since I got the device. Oh and my 40 bpm resting hr? Yep the TriHRM like all Garmin HRM's doesn't activate until over 80bpm. Useless for anyone with a good heart, because a low intensity workout may not bring our hr up enough to pop the straps min hr threshold. It's useless for those of us with a good heart trying to record pre/post workout hr's and also for warmups and cool downs.

Why doesn't the strap start working as soon as it detects HR, if I put the strap on I want it to record hr or I wouldn't have put it on in the first place? Why is there an 80bpm threshold? Probably because this cheep garbage can't detect hr under 80bpm.

It's not a battery thing unless you all are wearing your HR straps around as a fashion accessory to look cool when not working out? No? Are not a retard trying to look cool? Ok then. The device should detect HR when put on no matter what the HR rate. NO ONE wears a chest strap around that DOES NOT want hr recorded... that's why they put the strap on in the place; to record god damn hr. Why do you think they put the chest strap on in the first place you morons? It feels good? Moral support? Fashion? Garmin is run by Idiots.

My resting HR is set to 52, max to 197 with zones according to Karvonen method and adjusted for LTHR.
My HRM-RUN works great way below 80bpm.
I’m sure the IM worked on the old firmware before I updated. (Very old, like 4.30 or something.) But I updated the same day I bought it... however, I got some intensity minutes before I updated.
I’m no noob, I should have gotten about 1000-1500 intensity minutes last week if it was measured like the Fenix 3 always has.

Did you happen to adjust your Activity Class at the same time? I don't know why, but when I adjusted my AC from a 3 to a 7 (I don't understand the AC, but I work out hard 3x a week), my IMs dropped to a zero. I was holding my MaxHR over 150, but no IMs. When I dropped the AC back to a 3, my IMs skyrocketed.
When I asked CS about my Vivosmart not recording my IMs, I was told I wasn't working out hard enough. When I explained that I keep my HR over 150 for around 20 minutes, I was met with crickets.
Try adjusting your Activity Class and see if that changes your IMs.

Because auto detect doesn't work right on this $700 fitness tracker that's been around for 9mo the market.

umm, no. It's because very few people hit their maximum HR's during training or even racing. Autodetect reports the highest HR you have ACHIEVED, not the highest HR you are CAPABLE OF.

Even if I adjusted the Activity Class I would get some intensity minutes just from walking around.
On top of that, my job is VERY active. I often walk 20.000 steps during a day and I jump up and down on train cars, lift heavy stuff (half my bodyweight) and do work getting me into HR zone 3.
Come on now guys, IT'S NOT ABOUT LACK OF ACTIVITY.
THE WATCH IS RECORDING 0 (ZERO) INTENSITY MINUTES WHEN THERE WOULD HAVE BEEN MORE THAN 1000 (ONE THOUSAND) ON MY FENIX 3.
I'll try to wiggle some settings and see if it comes "unstuck".