No weekly intensity minutes for Zwift activities

Wow, this was more complicated to understand that I could have imagined. Thank you guys!

So just to give a update on the situation:

I did pair up the Garmin HRM Pro Strap with my iPhone and after the activity I was clearly able to see that Garmin Connect did show to items syncing: the Fenix 6X and the HRM Pro. After that the situation is unchanged and it is pretty hideous. Two activities with every detail imaginable, and 0 IM's. Clearly a bug on Garmins side that appeared sometime in August this year.

Could you post the daily HR graph for the 29/9?

Everything there, no IMs.

I just tested it with my HRM-Pro, and it still does work as advertised, counting the IMs correctly:

I removed the watch from my wrist (I did not start any activity on it, of course), put on the strap, assured myself that the HRM-Pro is really connected to Garmin Connect (looking at the status after taping on the device icon), and then did a ~10+ minutes long workout at almost double of my Resting HR. Unlike with the watch, the HR, steps, and IM values do not update in real-time while using the HRM-Pro, but once I finished, I pulled down the My Day screen, forcing the sync, and the values updated - I got 21 IMs (at double of the RHR, you get "vigorous" IMs, counting for two standard IMs).

So if it does not work with your HRM-Pro, then it either was not really connected to Garmin Connect during the workout, or it was not synced. Try repeating the same test as I did, assuring yourself that the strap is permanently connected (must be literally showing the status "connected" all the time), and does not lose the connection because of some battery optimizing options of your phone.

The firmware version is 8.80, on my HRM-Pro

I'm having trouble with hr and intensity minutes with Venu 2 plus as well, pretty much only happens when on zwift. Watch is only a few months old and it worked fine until recently. Garmin support basically told me the watch wont track hr on zwift because I hold handlebars. They kindly sent me HRM Dual but it doesn't track intensity minutes from zwift either. This is crazy I can't believe all these fancy garmin devices won't perform some of their most basic functions. 

Nicholas_Benn said:

Garmin support basically told me the watch wont track hr on zwift because I hold handlebars.

That's nonsense. Holding on handlebars has only impact on counting of steps at non-cycling activities, and does not influence the HR reading in any significant way.

Please post a link to the concerned activity, and a screenshot of the all-day heart rate graph for the same day.

I don't know, I have had notoriously bad Optical HR when biking or on my indoor trainer if I forget my Strap or something casual like a rental bike downtown, I always figure 'oh my arm is fairly still and watch is tight, should get good data'... then it is the same old junk (235 and 945 watches).