New Garmin connect Calorie issue?

You should not calculate the BMR from the "Resting calories" in Health Stats >> Calories, but from the value of "Goal" in the menu Calories In/Out. I suspect that the problem might be there. As I wrote, my results are all right even after Dec 14th, so I do not think the problem is with the application, rather with some of the input data.

I don't know what to say. I haven't adjusted anything in the apps and my personal data is accurate. 

Before my run yesterday morning, my Calorie count was 600ish, i ran 14km which showed 932 calories burnt. After the run my Calorie count still only showed as 1100. It should have showed 1532, even if it added the calories to my base count, or what ever. It disgarded 400calories from that activity alone into the unknown. Similar in the afternoon when I ran, it only added approx 300cal to my overall daily count and disgarded the other 364.

As I say. I'm just baffled as to what changed in my system on the 14th, that totally changed the way that it added my activities calories to the overall count. 

So, what is the "Goal" value in Health Stats >> Calories on Dec 28th and what it was before Dec 14th. Perhaps it can give us some clue?

And I mean the Goal value in Health Stats >> Calories of Garmin Connect, and not in another application that you seem to be showing on the screenshot above

I never had a 'goal' set-up. The calories in/out on 'connect' asked me to install the 'myfitness' app, which I didn't really want to have another app on my device, so I never bothered with it. I only installed it this morning to see what it said. It asked me to manually set a daily calorie target, which seemed a bit arbitrary as I set it to what ever I wanted.

I did set it at 1500 though, just based on what your value was as a lead. 

OK, sorry, that was then a wrong tip. Could you try to make a short activity without the HR belt, just having the HR properly monitored directly with the watch, and to see whether there is any difference? Something is definitely wrong with the input data for the BRM calculation, so let's exclude that it is due to the HRM belt-watch link.

OK, a walk around the local park with just the Fenix 5s HR Reading. 

Couple of km, a big steep hill down and back up in the middle, casual pace. 

Screenshots of HR/elevation, activity and daily calorie. This is at 7.30am, so that's why they're all so low. 

Yes, it looks as bad as before. With 152 Cal burned during 41.5 minutes, after deducing the BMR Calories, it should give around 93 active Cal alone for the walking (plus some smaller amount for the unlogged activity that morning).

Could you post some data before Dec 14th, when it was still OK, so that we can compare it? 

Also - you already wrote that you did not change any personal info like weigth, height, age, so I guess it is the same for the Activity Class that I see is set to 0. Maybe you could try setting it higher. I guess that a class of 7 to 9 would better correspond to your level. I do not really expect it could help with this issue, but perhaps it is worth of trying.

I crosschecked again my own data before and after Dec 14th, and they all give consistently expected results. That brings me to the suspiction that the active calories calculation is perhaps not done on the Garmin Connect server (or in the application), and that it is perhaps calculated directly in the watch and then passed over, already calculated. If it is really that case, I would first at all verify directly in the watch settings, whether all the personal data are correctly set there too. And if nothing odd is found that could be corrected, then I'd try factory reset, and setting it back from the scratch.

Another possibility would be trying some activity with another borrowed or a rented Garmin watch, temporarily linked to your account. Perhaps in your local store they could rent you a cheap Garmin model for a few hours, or you could even buy it, and return after the test. That would tell you definitely whether there is a problem with the Garmin Connect account, or with the watch.