to share on facebook WooCommerce product do not shows image

Hola! Mi problema es que al compartir en facebook los productos de mi tienda desarrollada con woocommerce, no se muestra ninguna imagen. Tengo el plugin Seo de Yoast instalado, y he probado a elegir con él una imagen. No funciona.
He probado con el plugin Facebook Open Graph, anulando la opción social de Yoast, y tampoco. Este plugin me devolvía el error: Error: Facebook Open Graph Tags cache NOT updated/purged.
Facebook returned: Object at URL ‘https://xxx.com/xxx/xx/xxxx/’ of type ‘website’ is invalid because a required property ‘og:title’ of type ‘string’ was not provided.
Después fui a https://developers.facebook.com/tools/debug/ y al introducir la url del producto me devolvía el siguiente error: The ‘og:type’ property is required, but not present. y The ‘og:url’ property should be explicitly provided, even if a value can be inferred from other tags.
Probé también con otros plugins pero ninguno me funcionó… ?alguna idea? Tengo wordpress 4.1.1 y Seo Yoast 1.7.4

Hello! My problem is that when share on facebook my store products developed with WooCommerce, no image is displayed. I have the Seo Yoast plugin installed, and have tried to choose a picture with him. It does not work.
I tested the plugin Facebook Open Graph, overriding social option Yoast, and neither. This plugin returned me the error: Error: Facebook Open Graph Tags NOT updated cache / Purged.
Facebook returned: Object at URL ‘https://xxx.com/xxx/xx/xxxx/’ of type ‘website’ is invalid Because a required property ‘og: title’ of type ‘string’ was not provided.
Then I went to https://developers.facebook.com/tools/debug/ and enter the url of the product I returned the following error: The ‘og: type’ property is required, but not present. and The ‘og: url’ property Explicitly Should be provided, even if a value can be inferred from other tags.
I also tried with other plugins but none worked for me … any idea? I Yoast Seo wordpress 4.1.1 and 1.7.4
Gracias