Why does not the file_field of my form build me? Rails

I'm trying to create a polymorphic association with Nested attributes in Rails, but my enemy here is Devise, which is not allowing me to build my file_field within my nested, and as a consequence it does not show me the option to select my image, I leave my full gist so you can see my main code:

link

I hope you can help me friends, greetings!