Avatar creation failed:
Ambiguous Transform ‘Armature/Hips/Spine/Chest/Neck/Head’ and ‘Head’ found in hierarchy for human bone ‘Head’. Transform name mapped to a human bone must be unique.
As of Unity 2022, GameObjects in your hierarchy cannot be named the same as human bones in your model’s humanoid rig. Some VRChat bases commonly name the body mesh as Head.
Change the name of the Mesh/GameObject that is causing the issue. In the above example, rename the Head mesh to another name in Blender.
If you continue to have Humanoid errors, try Humanoid avatar must have head, hands, and feet bones mapped.