Not workgin

Comment out line 107 and 189 in class/class-manage-discount.php:

//if($isFlatDiscountOn == 'no') {
// }

if you want to update prices automatically on product save add a metabox from line 191 and on:

function woocm_cat_add_meta_box() {

	$screens = array( 'product' );

	foreach ( $screens as $screen ) {

		add_meta_box(
			'woocm_cat_sectionid',
			__( 'Woocommerce Fields', 'woocm_cat_textdomain' ),
			'woocm_cat_meta_box_callback',
			$screen
		);
	}
}
add_action( 'add_meta_boxes', 'woocm_cat_add_meta_box' );

/**
 * Prints the box content.
 *
 * @param WP_Post $post The object for the current post/page.
 */
function woocm_cat_meta_box_callback( $post ) {

	wp_nonce_field( 'woocm_cat_save_meta_box_data', 'woocm_cat_meta_box_nonce' );
	echo '<div style="display:none">';
	list_category_bulk_discount();
	echo '</div>';
}

/**
 * When the post is saved, saves our custom data.
 *
 * @param int $post_id The ID of the post being saved.
 */
function woocm_cat_save_meta_box_data( $post_id ) {

	/*
	 * We need to verify this came from our screen and with proper authorization,
	 * because the save_post action can be triggered at other times.
	 */

	// Check if our nonce is set.
	if ( ! isset( $_POST['woocm_cat_meta_box_nonce'] ) ) {
		return;
	}

	// Verify that the nonce is valid.
	if ( ! wp_verify_nonce( $_POST['woocm_cat_meta_box_nonce'], 'woocm_cat_save_meta_box_data' ) ) {
		return;
	}

	// If this is an autosave, our form has not been submitted, so we don't want to do anything.
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
		return;
	}

	save_category_data();

}
add_action( 'save_post', 'woocm_cat_save_meta_box_data' );