Can't get pressure sensitivity to work on HP Envy x360 with active pen

I can draw with a brush, but the pressure sensitivity doesn’t work, the brush just stays the same throughout even though I’ve turned on the dynamics to pressure size. I’ve tried changing input devices, but the only thing available there is “core pointer” and I can’t see a way to add any other device. Does the pressure sensitivity only work on graphics tablets?

Well here is an explanation…