Problem retargeting animations

I have two skeletal meshes, one from Mixamo and other from the UE4 content samples.

I follow the steps for retargeting different skeletons (adjust skeletal settings for Humanoid Rig on each Skeletal asset, even adjust advanced translation retarget in skeletal tree), but when i “duplicate anim asset and retarget” in the animation, my skeletal meshes doesn´t appear in the window (ind if i try the retarget button i get the message about Preview Mesh setup).

Thanks in advance!