Imagen destacada wordpress

?Hola! tengo un problema, tengo instalado el tema Uncode(themeforest) el cual me permite agregar imagen destacada a mis post automaticamente,pero me muestra solo las imagenes destacadas si son imagenes grandes, si la imagen es peque?a (aproximadamente 1500 de ancho) no la muestra, alguna idea?
Hi! I have a problem, I have installed the Uncode theme (themeforest) which allows me to add featured image to my post automatically, but it shows me only the featured images if they are large images, if the image is small (approximately 1500 wide) it does not show it , any ideas?