Hey! I figured it out!
It’s just how I had everything wired in. Like a dummy, nothing was connected correctly.
This is it originally was plugged in and why it failed.
And this is how it should have been plugged in. Now I can toggle the IsAiming variable in the animation blueprint perfectly.
To the left of “Cast to FPS_AnimBP” is the “Event BeginPlay” node and to the right is the rest of my character controller.
Hopefully anyone else with this issue can see this.