I am trying to import an fbx downloaded from Mixamo but it won´t let me in any of it´s versions. I have alredy tried de Autodesk converter but nothing changed.
Without the fbx file there’s no way to know what the problem is just from that error message, though it seems to indicate that your fbx has no data.
You may see (and/or show us ) a bit more if you follow this part of docs.blender manualtroubleshooting crash …
More logs can be obtained by…
You may also check the FBX for example in/with the free Meshlab…