A small conflict exists between WooCommerce Wholesale Order Form and the Instagram for WordPress plugin (found on WP.org here).
The issue is to do with how fancybox is queued and the two plugins appear to clash, producing a JS error that can disable parts of the form.
The work around is easy enough, just pop the following code into your functions.php file in your theme:
add_action( 'wp_enqueue_scripts', 'dequeue_wwof_fancybox', 99 ); function dequeue_wwof_fancybox() { wp_dequeue_script( 'wwof_fancybox_js' ); }