Basically, after installing the OS update, F*/special keys were dead. Solution:
- Open System Preferences -> Bluetooth
- Click on the X icon to the right of the keyboard, in order to un-pair it.
- turn the Kinesis off, then on again, and press the CONNECT button at the back of the keyboard
- The keyboard should pop on the screen, select it and pair it again (you will have to type a few numbers shown on screen)