A good start here might be this, does the same problem occur using other software programs, you get use with pen yet no pressure sensitivity? If you have not tested this with other programs try the GIMP. You can download for free and install to test with that program.
I know the GIMP is a program that should run with pressure sensitivity. If the same problem occurs with the GIMP try Krita and MyPaint.
If same problem occurs with them you have a tablet that is probably running on the generic Windows driver for tablet pens, in other words your graphic tablet driver is installed yet not working. If the problem only occurs with Photoshop yet runs properly with GIMP, Krita, and/or MyPaint there is a flaw in the driver you are using where Huion failed to incorporate the version of Photoshop you are using into the driver. When you have a driver for a graphic tablet that is not working properly with pressure sensitivity you have no support from the graphic arts program and/or tablet manufacturer. Years ago I had a Wacom Intuous tablet that would never allow the feature of pressure sensitivity using Corel Photo Paint. Any other program that had support for Wacom worked fine, yet despite the Photo Paint tablet adjustment feature it never worked properly. Warning, for this test please use the suggested graphic arts programs I have mentioned, GIMP, Krita, or MyPaint. There are a lot of other graphic arts programs that only work straight with no pressure sensitivity available no matter what tablet you are using.
From here when you identify the source of the problem notify Huion, they may be able to create a new driver to fix the problem. Again you might try alternative drivers they have available, such as earlier or later releases, for your circumstance being you mention the tablet is two years old I would start by trying the oldest driver they have available and work back to the latest. For the hell of it you might even try a driver they have for other tablets that have similar features to the model you are using.