Most likely you have overtightened your Orbitkey. To resolve this you need to twist one side of the band anticlockwise for ONE full rotation while holding the other side of the band stationary.
Another method we can suggest is have your forefinger supporting the shaft (side with the OK logo), and anchor your thumb, and middle finger by holding down the side of the leather on the screw side, while you try and unwind the screw with a coin (facing you).
See video links below:
This is for our version 1, but will work with version 2 as well.