Hi,
So I've been having issues with trying to add my fenix 6 since I've purchased it. I've been in contact with Garmin Support but they were unable to figure out what my issue is, since they couldn't reproduce it.
The symptom is that when I try to add the device, it pops up a login prompt to connect to my garmin connect account and after I provide the correct credentials, it just fails with a generic error message about can't connect to garmin servers.
I've looked at the application logs and every time I try, it has a BadRequest error after the successful authentication.
I've been searching online an playing around with reinstalls, always on the latest version of Garmin Express, but nothing helped, until today, when I had an idea, and it worked! I changed the Regional format settings from Hungarian to English (United States) in Windows and Garmin Express could add the watch right away. It must've been some number or date formatting that has caused the issue for me that the app uses system settings for...
I'm not sure if any other locale formats are affected, but if any international users are experiencing this, it's worth a try until they fix this bug. (I wrote an update to support about my finding)