I just don't find it reliable. Sometimes it works, sometimes it doesn't. I have a MacBook Pro (mid-2015), an iPad Air 2, and an iPhone XS. I've tried logging all of them out of the same iCloud account, restarting, and then logging them in again, but that only seems to work for a while. Both iOS devices are running iOS 12.0.1, Wifi and Bluetooth are on, the devices are near each other. Does Mojave improve the reliability?