Jetpack Open Graph Meta tags are automatically disabled if you already use another plugin that supports Open Graph tags. The full list of these plugins is available here.
However, in some cases you might prefer to use Jetpack’s Open Graph tags, even if your other plugin offers such functionality. To do so, you’ll have to reactivate Jetpack’s tags by adding the following code to your theme’s functions.php file, or to a functionality plugin:
add_filter( 'jetpack_enable_open_graph', '__return_true', 100 );