Yeah so the thing is, your model needs to have a root component that is on the ground in order for root motion to work. And not just that, you also need that critical component for certain IK setups as well.
You can fix this by creating a socket from hips (which is what your root is, I presume, since it’s from mixamo) and adjusting the bone hierarchy accordingly but adding a proper one from Blender would be better!
Yep just double checked, that hip socket approach made my IK legs work but not root motion, you would need an actual ground anchored root for that.