I have checked all the screen options tab and the post meta box for entering featured image does not appear.
But something is strange, because when I close the window, the first three ones are disabled again.
It´s not an accident, they are automatically disabled when the window is closed
Imagen de la diapositiva (940×200)
Link de diapositiva
I sent the credentials of my wordpress to Daniel Jones, if you could see inside.
Thank you in adavance