Hair defaults to sticking straight out, and the dynamics moves it from there. I'd like to comb it to something more reasonable so the dynamics don't have to do as much work. The problem is that once I change something, the dynamics stop working entirely. How do I fix this problem?
Hair dynamics can use edited particules, something is stopping the normal process.
As you edited the particles, you're probably in particle edit mode.
This mode allows you to edit your particles but does not allow simulation Go to object mode to start your sim.
Your simulation should be playing correctly with edited particles.