Sort WP_Query with numeric custom_field

Hi Folks

I have added a numeric field (called ‘video_order’) to a certain post type, via ACF
I would like to sort the list of posts, by that numeric field.
I have made sure to go through the posts and give them all a value.

This is the Query i have tried, which does not seem to work.

Can someone suggest something?

Thanks!

$args = array( 'post_type' => 'post_sermons','post_status' => 'publish', 'posts_per_page' => ot_get_option('wpl_sermon_per_page'), 'paged'=> $paged,'orderby' => 'video_order', 'order' => 'ASC' );