I have successfully used Garmin Connect Mobile in the past on a Lumia 640 running the last version of Windows 10 Mobile. I used the app to create a user profile, pair with the vivofit 3, interact with my dashboard, and after a bit of trial and error I figured out how to get it to sync repeatably and reliably.
However, I recently tried to use a Lumia 650. I logged in to my existing user profile, and I was able to pair with my existing tracker. But then I was dumped on the "Devices" page. There doesn't appear to be any way to get into the dashboard.
The dashboard doesn't have a link in the "menu" button. I've tried exiting and re-launching the app. I've tried rebooting the device. No matter what I do, the app always just launches directly into the Devices page and there is no link into the dashboard.