Hi,
According to the user manual, the GPS is automatically turned on or off depending on which activity is chosen. Apparently not all activities have GPS access. It is also turned off for indoor activities.
Here is an image, taken from the user manual which shows how to select "Glonass". Be aware of the '''note''' in the image and select an appropriate activity to enable you to have both GPS and Glonass working. (Click on the image to enlarge it for better viewing)
[image|908552]
Here is a link to the user guide for a Vivoactive HR.
http://www.clevertraining.com/images/product_manuals/VivoactiveHRManual.pdf