I have scoured the net for a while looking into the bluetooth problems with High Sierra and my macbook mid 2012. It stopped working as soon as I went to High sierra, is disappeared from system information - so it looks like there is no bluetooth device at all. It was definitley working perfectly until the upgrade. I have tried many of the tricks including deleting the bluetooth .plist file, reinstalling the OS, opening up the mac to check all the connections are good. An upon looking on the internet there appears to be a thread about this issue here: https://discussions.apple.com/thread/8129665?start=90&tstart=0 Now, I might have missed a big conversation on these forums here so if I have please point me that way, but its obviously a problem for many older macbook users. I am reluctant to throw away my macbook as its an i7 with 16gb ram SSD drive etc, so not a bad computer and works well with the music stuff I do. But I use a Korg keyboard that connects with Bluetooth that I use a lot so I really want bluetooth to work. So has anyone any idea where things are with this? Im not trying to blow my own trumpet but I am an IT field engineer so I have some troubleshooting skills under my belt and I have tried everything I can think of and it feels to me like High sierra has either: 1. Damaged, changed the firmware in the bluetooth. 2. Problem with drivers 3. Some users not having issues may have a different bluetooth controller - my mac was refurbished through apple, is there a chance they put a slightly different bluetooth card in there? 4. It has actually died in a very unlucky coincidence.