An error has occurred message when looking at fitness age.

I have the same problem,  there is a pop up with error and the average days of the activity are incorrect. I wrote to the support, but I didn't receive response

Well they replied, Ive sent over a diagnostic, and screenshots as well as a link to this post, its now been passed on to engineering for investigation

I also had this error.  I removed the app and reinstalled it again adder my watch and now the eror is gone.  The thing is that I also had an old device registered together with the new watch on the old Installed app that I now don't have anymore.  Maybe that is the issue.  do others Who have the fault maybe also have multiple devices in tthe app?

I have error with only one devise in the app

I'm seeing the same thing. I am on version 4.65.1, but the error has been popping up on fitness age for weeks now (maybe since daylight savings time ended). I don't look at weight much, but I checked it, and the error pop-ups are there, too.

It doesn't seem to have a practical effect on anything; it's just annoying.

It has a pratical effect in fitness age... why activity days aren't numbered correctly

Same error here for fitness age and weight. Weight data seems to work OK. Age does not. Says Vigorous days 4 wk avg, 0 days per week. Should be 3 or 4. The error message has been popping up for several weeks but only in the last few days have the reading been incorrect.

Update about 4 hours later: I uninstalled and reinstalled the Garmin Connect app. Both weight and fitness age are error message free and reading correctly. I did not clear data so other than logging in all of my settings and devices remained.

I can confirm this. Uninstalled and reinstalled the Connect app just now and the errors have disappeared, thanks for the suggestion!