Avatar Creation broken

I am attempting to create a VRChat avatar based on a model my father made in Blender. I am trying to cooperate with Unity's system, but it is not working. I select the object (fbx file) to be humanoid, which of course has errors, so I go to configure the model. After a painstaking amount of attempts trying to optimize the bone structure, it simply doesn't work. I assigned the correct parents/ancestors/children to each bone as accordingly. However, it still says they have incorrect parent/children assignments. For example, the error message I receive when I try to apply changes says "Transform 'LEG LOWER.L' is not an ancestor of 'FOOT.L'."
Then, if I try to apply my changes and leave configuration anyway, it resets all of my progress, as if I changed nothing. I even tried getting the newest update of Unity, with no luck. I tried modifying the model/bone structure in Blender, and still nothing.