I synced my 645 music this evening and could not find any heart rate data before 6.06 pm. both in "Daily summary" and in Heath Stats --> Heart rate.
This is very strange since I did strength training at 5.32 pm. When I check the activity section it clearly shows heart rate data.
This means the watch recorded my heart rate, perhaps the whole day while I was wearing it, but somehow not showing it on daily summary or heart rate section. For some reason it only shows the data from 6.06 pm. onward. There is also no sleep data for last night despite me wearing the watch all the time.
I tried disconnecting the watch from my phone and resyncing it but still can not solve this issue. I checked other threads and saw that some had issues about the watch only recording data during activity and not during resting. Mine, however, seems to be recording all the time but there is just no way to view it.