WordPress SEO by Yoast ignoring Facebook Descriptions

Hiya - if this is nothing to do with the theme apologies and I'll keep googling.
This SEO plugin lets you type in different descriptions for sharing on Facebook but on this one website it is being ignored on here.

I added some code to the functions.php file to stop Jetpack using it's OG data so the SEO plugin would have priority. It hasn't made any difference though.
I've removed the trailing / on the permalink - no difference

This bit of googling mentions the header file and says this is missing when someone else had the same problem, it's the description that is missing on mine though

<title><?php wp_title(''); ?></title>

https://wordpress.org/support/topic/...rking-properly

I don't want to go messing around with the theme because I really do not know what I am doing here.

I've spent literally hours on this and can't work out what is going on! Any ideas much appreciated.