I added som extra parameter DON'T FORGETT to change app_id
{if $page_name=='product'}
<meta property="og:type" content="product" />
<meta property="product:retailer_title" content="{$shop_name|escape:'htmlall':'UTF-8'}" />
<meta property="product:brand" content="{$product->manufacturer_name|escape:'htmlall':'UTF-8'}" />
<meta property="product:pretax_price:amount" content="{$product->getPrice(false, $smarty.const.NULL, 2)|round:'2'|escape:'html':'UTF-8'}" />
<meta property="product:pretax_price:currency" content="{$currency->iso_code}" />
<meta property="product:sale_price" content="{$product->getPrice(true, $smarty.const.NULL, 2)|round:'2'|escape:'html':'UTF-8'}" />
<meta property="product:price:currency" content="{$currency->iso_code}" />
<meta property="product:weight:value" content="{$product->weight}" />
<meta property="og:image" content="{$link->getImageLink($product->link_rewrite, $cover.id_image, 'large_default')|escape:'html':'UTF-8'}">
{else}
<meta property="og:type" content="website">
<meta property="og:image" content="{$img_ps_dir}logo.png" />
{/if}
<meta property="og:title" content="{$meta_title|escape:'htmlall':'UTF-8'}"/>
<meta property="og:site_name" content="{$shop_name|escape:'htmlall':'UTF-8'}"/>
<meta property="og:description" content="{$meta_description|escape:html:'UTF-8'}">
<meta property="fb:app_id" content="YOUR ID" />