Sorry unable to map your existing skeleton

Hi Mixamo Community! 

This is my first post here and I want to ask for your help.
I've been trying to load my model into Mixamo to animate it for a few days now, but every time Mixamo gives the same error. I have already tried to compress the FBX file and upload the compressed version, but the result is always the same. I also uploaded my model as an OBJ file, but the animation doesn't work correctly. I am just starting my way in 3D and don't understand a lot, could you please take a look at my project and give some advice? Thank you all in advance.