I downloaded the recent firealpaca and now it won't do pressure. It just look like a boring line. I made sure the pen pressure box was checked. It still didn't work. When I doodle on something else the pen pressure is just fine. I am getting really frustrated.
In the environment settings (ctrl/cmmd+k), try playing around with these features here:
See if that solves anything (try one at a time before changing multiple things).