@TIG
I did what Rich-O-Brien said, running th repair as administrator, with the sketchup closed. But nothing's changed. It keeps showing B03 when I first click on "activate license", and A04 when I apply my license file, which is in my "C:-users-profile name-desktop" route.
Has it got to do with me recently changing the PC's name? I've been using the rubies for a while before I changed my desktop's name in the windows system setting.