Having issues in saving with Ruby on Rails

I'm trying to make a todo list with Rails, first I have made the List and it's specs, everything went okay, but then I've began to make it's items, but it simple don't save it's content, it stores a empty string, it don't work neither on the form or on the specs. When I try to save with the Rails console everything goes okay.

This is the message I receive from Rspec:

Creating todo items is successful with valid content
 Failure/Error: expect(page).to have_content("Ruby")
   expected to find text "Ruby" in ""

Above is the code for...

#todo_item_controller.rb

class TodoItemsController < ApplicationController
  def index
    @todo_list = TodoList.find{ params[:todo_list_id] }
  end

  def new
    @todo_list = TodoList.find{ params[:todo_list_id] }
    @todo_item = @todo_list.todo_items.new
  end

  def create
    @todo_list = TodoList.find(params[:todo_list_id])
    @todo_item = @todo_list.todo_items.new(todo_item_params)
    if @todo_list.save
      flash[:success] = "Added todo list item."
      redirect_to todo_list_todo_items_path
    else
      flash[:error] = "Something went wrong"
      render action: :new
    end
  end

  private
    def todo_item_params
      params[:todo_item].permit{:content}
    end
end

#index.html.erb

<h1><%= @todo_list.title %></h1>

<ul class="todo_items">
  <% @todo_list.todo_items.each do |todo_item| %>
    <li><%= todo_item.content %></li>
  <% end %>
</ul>
<p>
  <%= link_to "New Todo item", new_todo_list_todo_item_path %>
</p>

#new.html.erb

<%= form_for [@todo_list, @todo_item] do |form| %>
  <%= form.label :content %>
  <%= form.text_field :content %>

  <%= form.submit "Save" %>
<% end %>

When it appear on the browser it displays only the list symbol but no content.

Sorry for too long