[AC Question]

TrackR bravo devices are supposed to connect (using Bluetooth 4 LTE) directly through the TrackR app without having to go into the Bluetooth settings. It works on other phones, it works on my ASUS tablet. But on my UK unlocked HTC One M8 running Android 5.0.1 the app sees the TrackR device but won't connect to it.
I've tried it with and without SmartLock, I've uninstalled security apps that might be interfering, Nothing works.
I've searched here and generally on the web for HTC One M8 and TrackR - without success.
Any ideas?