This is just because you didn’t select the Mannequin skeleton when you imported your model, Mixamo states there skeleton supports unreal 4 which it did when the blue Mannequin was still being used, Just re-import it and select the Mannequin skeleton, If you plan on using the unreal animations you will still need to tweak the bone locations on your Mixamo character other wise just import some animations off the Mixamo site.
Also what are using for your ranking system? is that a marketplace asset?