Try this: Go into your Garmin app open "More", open "Garmin Devices" delete your device first. Next "Add Device" You won't loose any saved activity info and it should upload your stored info from your device during down-time.
I have my 735XT already open to this setting...(other devices may be slightly different) Menu, Settings, Bluetooth, make sure status is connected, go to Pair, complete the above, confirm 6 digit pairing prompt ......BOOM!
I hope this works for someone/everyone.
YEP That worked. had to do a hard reset today. Something was locking it up and not working.