maybe unity support perfect!
I’m not sure but maybe the problem is because your FBX contains more animations. I have tried to import your FBX into Unreal Engine and it couldn’t too, it gives this information:
Maybe when you export the model you have to change the Options/Include settings.
If it solves your issue maybe you have to modify the texture source too, here you can find some information about that one: Do you know any 3D game assets marketplace for Heaps?