If you are having problems with pressure, one great diagnostic test you can run is to try testing the pressure in the tablet driver itself.
Most tablet drivers have some kind of "pressure test region" where you can try out the pressure. Usually this pressure test region is found close to the UI for defining the pressure curve.
There are two locations in the Wacom Tablet Properties app where you can see the pressure.
First, you can see the pressure under the Pen tab. It is shown in the Current Pressure bar.
Second, you can also click Customize which will bring up the Pen Feel Details dialog.
Here you can draw in the Try Here section and see how the pen draws with pressure.
Open the HuionTablet app. Then navigate to Digital Pen > Pressure Sensitivity Adjustment.
Draw in the Pressure Test area.
Open the Xencelabs app, then select the pen you are using, then draw in the region to the right of the pressure curve.