Having a BT problem I first open a Terminal / Konsole and run as root:
If BT device is recognized, you see a hex code and the name of the device.
Sometimes it is necessary to disable BT by hardware, enable it again.
If you can start BT: the adapter must be "always visible".
BT is a big problem on many Linux distributions (and Windows!)
To find out if an adapter is present:
00:12:5A:6B:18:46 Bluetooth Notebook Mouse xyz
hidd connect --00:12:5A:6B:18:46
Maybe you get:
The program 'hidd' is currently not installed. You can install it by typing:
apt-get install bluez-compat