https://apps.garmin.com/en-US/apps/da3db127-3938-4dac-bcf1-e30324fd0d20
The whole app settings logic is a part made by Garmin.
As a developer, I do not have any influence on this part of the app/widget.
What I experienced:
As long as the widget is newly installed or updated, I can safe app settings using my iOS device.
As soon as I safed app settings using my desktop version of garmin connect once the connection between iOS and the devices app settings (fenix3 in my case) is permanently broken.
In other words, if I use garmin connect on my win10 desktop once to write app settings, I can not witch to the smartphone app anymore. (because of the access denied bug)
I have no idea why!