Hi there,
I’ve tried many things to get this working, the support unfortunately didn’t help, I tried re-connecting my Bluetooth device, it’s a Bluetooth fm transmitter for my car, km20 to be specific. Anyways reconnecting it doesn’t help, I tried turning off WiFi and Bluetooth completely, restarting then turning back on and connecting to the device, didn’t help, I tried resetting the network settings, repeating the disconnect Bluetooth and re-connect, still no good.
My problem is that it disconnects randomly, sometimes it takes 10 minutes, other times 40, I notice this since I frequently drive for an hour each day, and having to re-connect it is a pain. This wasn’t a problem with iOS 10 or a Google Pixel I tried, just with my new iPhone 8 Plus Bluetooth 5.0 with iOS 11. I feel like my phone is trying to kill off battery draining apps, sort of like having Pokémon go and a Bluetooth headset connected, it would stop Pokémon go and keep my music going. Just a guess.