If you have the Atheros AR3012 (shipped in some lenovo laptops like the z50 that i have) and linux lite 4.0 or ubuntu 18.04, you might have a problem with the adapter, and if you use the command dmesg you are going to get this error:
bluetooth: hci0: don't support firmware rome 0x31010000
I found this solution that solve that issue...
1. Add the ukuu repo to your system:
sudo add-apt-repository ppa:teejee2008/ppa && sudo apt update
2. Install ukuu:
sudo apt install ukuu
3. Install the kernel 4.16.9 with ukuu:
sudo ukuu --install v4.16.9
4. And finally reboot
The problem with the AR3012 is caused by the kernel 4.15.0 shipped with Ubuntu 18.04 and linux lite 4.0 and the unique kernel i found that solve that issue is the 4.16.9
pd: i'm not an english speaker so maybe the instrutions or the grammar is bad, sorry for that