Adjusting fork preload on a Vado

[PaD]

Can’t move the adjuster knob on the top of left fork leg.
I have a Vado 4.0 but at least in Europe the 2.0 - 4.0 have the same Suntour NCX E25 fork. The knob is marked Preload and has arrows , clockwise for +, counter clickwise for -.
I just can’t move it. Is there a special technique for it?

 

[coffeemaker]

It's most likely stuck in one direction. Use pliers and a towel to loosen it.

 

[PaD]

It's most likely stuck in one direction. Use pliers and a towel to loosen it.

Thanks, I´ll try that. A little worried though that I might force in the wrong direction if it is stuck in an end position.