I18n definition, no translated labels

form.html.erb

<%= form_for(@user) do |f| %>
  <% if @user.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@user.errors.count, "error") %> prohibited this user from being saved:</h2>

      <ul>
      <% @user.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

    <table>
      <tbody>

        <tr>
          <th>
            <%= f.label :username %>
          </th>
          <td>
            <%= f.text_field :username %>
          </td>
        </tr>
     
      </tbody>
    </table>
   <% f.submit %>
<% end %>

nl.yml

nl:
  activerecord:
    models:
      user: Gebruiker
    attributes:
      user:
        first_name: Voornaam
        insertion: Tussenvoegsel
        last_name: Achternaam
        initials: Initialen
        gender: Geslacht
        username: Gebruikersnaam
        email: 'E-mail'