Most likely the shaft + screw mechanism has been overtightened. This can happen when there is no wave washer in with the keys, or the screw has been over-rotated into the system.
We recommend twisting one side of the band anticlockwise for ONE full rotation while holding the other side of the band stationary.
See video links below:
This is for our version 1, but will work with version 2 as well.
Another method we can suggest is have your forefinger supporting the shaft (side with the 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). Don't use a screw driver or any heavy tool, as this will damage the mechanism.