Showing Thumbnail for link in WhatsApp || og:image meta-tag doesn't work

Solution 1:

I belive you need to add itemprop to the og:image meta tag, have the image size set to 256x256 and also it would not harm to add the site_name, type and updated_time properties either :)

<meta property="og:site_name" content="San Roque 2014 Pollos">
<meta property="og:title" content="San Roque 2014 Pollos" />
<meta property="og:description" content="Programa de fiestas" />
<meta property="og:image" itemprop="image" content="http://pollosweb.wesped.es/programa_pollos/play.png">
<meta property="og:type" content="website" />
<meta property="og:updated_time" content="1440432930" />

You can see these meta tags in action on for example Google Maps.
After you have changed your meta tags, you might need to wait a while for possible caches to update.

You can debug/verify Open Graph meta tags from the Facebook Debugger
If you can see all your tags there, then the sites/apps where your tags are not showing properly might have different requirements for Open Graph tags.

EDIT:
If you are going to specify an image by a HTTP-Secure link, you need to use og:image:secure_url instead of og:image.

EDIT2:
You also need to specify og:type as it is one of the four base required parameters.
<meta property="og:type" content="website" /> should get you in the right direction.

Solution 2:

I had the same issue and the problem was the size of the picture. Whatsapp doesn't support picture with a size greater than 300KB.

So the most important property to display image on Whatsapp is:

<meta property="og:image" content="url_image">

And the size of the image to display must be less than 300KB