Dropzone ActionView::MissingTemplate

I put the codes in their respective places and added fomart : html to not seek json , but always the rails spits ActionView :: MissingTemplate : Missing template avatar / update , application / new with { : locale = > [ " en -US" , : us ] : formats = > [: json ] : handlers = > [: erb , : builder , : coffee ] } . searched in

someone have any tip? thank's

    $(document).ready(function(){

        Dropzone.autoDiscover = false;

      var logoDropzone = new Dropzone (".dropzone", {
            maxFilesize: 2, 
         maxFiles: 1,
          dictDefaultMessage: "Drop your images here",
            paramName: "user[avatar]",
            addRemoveLinks: true, 
       dictRemoveFile: 'Remover'
      });
});



def update
    @user = User.find(params[:id])
    if @user.update_attributes(params[:user])
      redirect_to(action: :edit, id: @user, only_path: true,format: :html)

    else
      render :edit
    end



<%= form_for(@user, :method => :put, html: { multipart: true, class: "dropzone"}) do |f|  %>

      <div class="fallback">

        <%= f.file_field :avatar %><br>
        <%= f.submit "Save" %>
      </div>
    <% end %>


  </div>