Hello,
I'm not sure if this has been mentioned, I tried searching but it kept giving me errors so I apologise is this has already been mentioned.
On the Garmin Connect app, whenever I try to set the main display on my Vivosmart as Heart Rate, once it says it has saved the changes the default display turns to "Last Screen Viewed" both on my device and when I go to change the display again. If I go to the display page again before saving the settings, the home screen says "page_none"
I'm currently using build version 2.7.4 on my Galaxy S5 Android version 4.4.2 and my Vivosmart has software 3.0, although I've had problems with this on earlier versions I believe.