Como sugerido no fórum Linux Mint , você pode tentar o seguinte:
-Change #AutoEnable=false to AutoEnable=true in the /etc/bluetooth/main.conf (notice new line is un-commented)
-Unpair the headset
-Restart the bluetooth service sudo /etc/init.d/bluetooth restart
-Pair your headset again and connect it
-Go to sound settings. From the output device tab you should now see the headset listed along with other output device like internal speakers
-Choose it as the sound output device.