I'm following this tutorial for neon effects in Illustrator: https://www.youtube.com/watch?v=zWSFGIEAz4s
However, whenever I offset the path, for some reason some of my letters remain filled in and some of them turn into outlines? I don't understand what I can do to stop this from happening. I can't have some of the letters filled in and some not - it doesn't work for the neon look.
I'm using Illustrator 2019, version 23.0.3. The only difference I have between the tutorial and my file is that I didn't start with a font, I started with a logo (which is just an outlined version of the font originally).
What am I missing?