Surface pen pro not working

MyPaint does not detect pressure sensitivity from my pen, and just reads it as a mouse. It works on all other applications.
I have a surface book.
I’m running mypaint v2.0
I’ve seen something about GTK demo, and while I know how to open it, I dont know how it would help.
I actually tried to use this software about a year ago, had the same issue, and gave up. I really would like to be able to use it for once.