On Android devices you must allow location access permissions and have the GPS turned on for the app to detect or connect to a sensor. This is intentional Android OS behavior from 6.0+. It is implemented for privacy reasons to prevent apps from tracking your location by scanning for Bluetooth beacons and WiFi points (which the developer knows the physical location of) and using this to track your location without ever asking for location permissions and turning on GPS.
See article below for how to do this: