That must be it. I will try that right now.
Embarrassing that I did not see that elsewhere....despite doing some Googling! I saw that the bottom buttons were working in other applications, and I thought the top button should work the same way....
I am under the impression that if I press the top button on the stylus, OneNote should launch automatically. When I press my button, nothing happens. I checked the preferences in OneNote, and all the correct boxes are checked.
Any ideas?