Bug - Heart rate zones not calculating on 840 using HRM-Pro

I've been having an ongoing issue with my new Garmin 840.

I've done 7 rides so far as the 'Time in Heart Rate Zones' is not calculating.

My heart rate monitor is a Garmin HRM-Pro.

In Garmin Connect, my activity will accurately show my heart rate values during my ride and will vary between zone 1-5 but the 'Time in Heart Rate Zones' will show either '0' for all zones.

I've tried to reconfigure all my heart rate zones but it hasn't made a difference.