How to apply Mixamo motion clips created for one model to another model with the same hierarchy

I want to apply a motion clip that was created with a Mixamo human figure animation to a robot model. The robot is not a single mesh but a collection of parented subunits. The robot components were parented to a T Pose rig from Mixamo, so it’s the same hierarchy as the walking figure. The assumption is that joints are joints, and so long as the hierarchy is maintained, I should be able to mix and match the motion clips from different characters. But I’m missing something because when I apply the motion clip to the robot rig, it doesn’t move - everything is frozen in the T Pose. Is there a setting that will unfreeze the T Pose and apply the motion clip?