Why is my form not sent?

I can not find the error of this; please help.

The images of the input is not detected.

<form action="core/models/publicar.php" method="post" id="user_publicate" enctype="multipart/form-data">
          <div id="Public_user_main_center_start" class="center" style="background: #e0e0e0;">
             <span contenteditable="true" id="Texto_publicacion_user_main" name="hola">Publica algo aquí</span>
             <output id="list"></output>

             <input id="background_color_main_publicate" type="hidden" value="#e0e0e0" name="background">
             <input id="Texto_publicacion_user_main_input" type="hidden" value="black" name="color_span">
             <input id="Texto_publicacion_user_main_imagen" type="hidden" value="" name="user_imagen">
             <input id="Texto_publicacion_user_main_texto" type="hidden" value="" name="texto_publicado_en_red">

          </div>

          <div class="down">
              <div class="publicate"><button type="button" onclick="publicar_main_red();"><i class="fa fa-globe"></i> Públicar</button></div>
              <div class="add_content">
                  <div class="diseno_back">
                      <div class="color color_red"><button type="button" onclick="background_color_main_publicate_color_red();"></button></div>
                      <div class="color color_darkred"><button type="button"  onclick="background_color_main_publicate_color_darkred();"></button></div>
                      <div class="color color_yellow"><button type="button"  onclick="background_color_main_publicate_color_yellow();"></button></div>
                      <div class="color color_black"><button type="button"  onclick="background_color_main_publicate_color_black();"></button></div>
                      <div class="color color_green"><button type="button"  onclick="background_color_main_publicate_color_green();"></button></div>
                      <div class="color color_darkgreen"><button type="button"  onclick="background_color_main_publicate_color_darkgreen();"></button></div>
                      <div class="color color_blue"><button type="button"  onclick="background_color_main_publicate_color_blue();"></button></div>
                      <div class="color color_lightblue"><button type="button"  onclick="background_color_main_publicate_color_lightblue();"></button></div>
                      <div class="color color_darkblue"><button type="button"  onclick="background_color_main_publicate_color_darkblue();"></button></div>
                      <div class="color color_orange"><button type="button"  onclick="background_color_main_publicate_color_orange();"></button></div>
                      <div class="color color_darkorange"><button type="button"  onclick="background_color_main_publicate_color_darkorange();"></button></div>
                  </div>

                  <div class="normal_add">
                      <!--button name="imagen" type="button" id="mostrar_imagen" onclick="mostrar_imagen();"><i class="fa fa-image"></i-->
                      <input type="file" id="files" name="files[]" multiple />
                      <!--/button-->
                      <button type="button" onclick="no_disponible();"><i class="fa fa-video-camera"></i></button>
                      <button type="button" onclick="no_disponible();"><i class="fa fa-music"></i></button>
                      <select>
                          <option value="publico">Público</option>
                          <option value="amigos">Amigos</option>
                      </select>
                  </div>
              </div>
            </form>

publicar.php

$POST_TEXTO_main = $_POST['texto_publicado_en_red'];
//imagen_publicada
if(isset($_FILES['imagen_publicada'])){
    echo "funciona";

}else{
    header('location: ../../?no-sepudo-procesar-los-datos');
}

always returns me to the header.