I have an LG G4 (running Android Marshmallow 6.0 on Verizon). My Pebble Time displayed call notifications quickly and reliably with this phone.
With my Garmin Vivoactive HR (running software 2.40), call notifications either do not appear at all, or not until after 4-5 rings (20-25 seconds after the phone starts ringing). Since my phone goes to voicemail within a few seconds of that, even when I get notified, it's too late to be of use.
This morning, I spent some time poking at it: reset/restarted, unpaired/paired, disabled/enabled BT on both devices, reset "Apps with usage access", etc. Now I'm not getting any call, missed call, or voice mail notifications (all enabled under GCM's "Smart Notifications", and I told the phone to allow access when I was prompted), but I am getting other types of notifications (such as SMS).
Before I contact Garmin tech support, does anyone have any suggestions?