Issues interfacing BP with materials

I’m trying to pilot a dynamic material instance using blueprint in order to color the characters when they perform certain actions, and while I’ve been able to change dynamic material instances parameters in static objects before, it seems animation blueprints won’t let me.

Here’s how I initialize the variable in the animation BP (tried with and without setting the material onto the mesh after making it dynamic)

And here is the test structure where I try and make the character blink red/green when he walks, using the anim notify I know work since I use them for footprints.

The material itself isn’t very complicated, but I’ll include it as reference.

And to be extra sure, here is how things look when the parameter is black, and when it’s forced to be red.