Pen Pressure Calibration

New to digital art and could do with some advice on how to get the pen pressure calibrated.

Using:

Windows 10

Corel Painter 2021

XP-PEN Star G960

Whatever combination of Pressure v Output I set in the XP settings I cannot get the Corel brush to vary according to touch pressure.

Even in the XP settings it is very difficult to get the output to vary linearly across pressure, mostly output goes to 100% as soon as you put pen to tablet.

Changing from Wacom to RTS, whatever they are, in Preferences/Tablet has no apparent effect.

Advice/guidance eagerly awaited.