Garmin Connect Calendar Issues - Not showing workouts in monthly view

Have you tested with different web browsers and in private/incognito mode (to make sure that no plugins/addons interfere)?

You can also try hard-reloading the page (hitting the Ctrl-F5 or Shift-F5 key kombination), clearing so the cache for that page. Or deleting the temporary Internet files.

Do you see the concerned activities on the Activities page?

Yep. It’s consistent across all apps to, but just monthly view, and is only for the months of Dec and Jan

Yep, activities are there, and viewable in yearly and weekly views.

Within the Connect App, monthly view is the only one available so cannot see there!

And did you try the forced reloading with Shif-F5 (alternatively with Ctrl-F5 too)? Clearing the browser cache?

Can you see the header with the month choice and Filter selection, when you select the Month view? Is the selecting of another month, or adjusting the filter working?

Force reload on my Mac doesn't do anything. 

I can see header, and filter with every other month, but not the months affected. Filter is working. And bizarrely, if I look at November in month view, I can see the first few Dec activities, but not in the December month view. It's very odd

What happens when you call directly the following URL for accessing the JSON data for December 2020? Does it show some data?

https://connect.garmin.com/modern/proxy/calendar-service/year/2020/month/11  

You can make the code better human-readable for example with the tool https://codebeautify.org/jsonviewer 

When I put in what you stated, all I get is 

{"message":"Course not owned or not found.","error":"BadRequestException"}

But if putting the previous months in, all is good.

I tried putting January in and got

{"startDayOfMonth":1,"numOfDaysInMonth":28,"numOfDaysInPrevMonth":31,"month":1,"year":2021,"calendarItems":[]} 
and then put Feb in and got

{"startDayOfMonth":1,"numOfDaysInMonth":31,"numOfDaysInPrevMonth":28,"month":2,"year":2021,"calendarItems":[]}

The one thing that jumps out, is the amount of days in jan being described as 28! Wonder if this has something to do with the GPS bug too.

RoadRunner... said:

The one thing that jumps out, is the amount of days in jan being described as 28! Wonder if this has something to do with the GPS bug too.

No bug, it is just the numering of months that starts with 0 (for January) and ends with 11 (for December)

What do you get for January 2021 (/calendar-service/year/2020/month/0), for Decemeber 2020 (/calendar-service/year/2020/month/11) and for Noverber 2020 (/calendar-service/year/2020/month/10)?

Just been playing more, and seem to have isolated it to the 2nd Jan. That week, and that day are not viewable, and there appears to a rogue 'event', on that day. I can delete the activity that occurred, but the event I cannot seem to find!