my custom fields not save in my edit product

hello all im make this code to put in my edit products but i dont know why the taxonomy dont saved in my post y share you my code i put all hooks and nothing change :

i put in products/variation product seccion becose i need to show in attributes seccion.....


<label for="brand" class="form-label"><?php esc_html_e( 'Brand', 'dokan-lite' ); ?> <i class="fas fa-question-circle tips" aria-hidden="true" data-title="<?php esc_html_e( 'Select the brand for your watch', 'dokan-lite' ); ?>"></i></label>
<?php
require_once DOKAN_LIB_DIR.'/class.taxonomy-walker.php';
$term = wp_get_post_terms( $post_id, 'brand', array( 'fields' => 'all') );
$selected = ( $term ) ? $term : array();
$drop_down_brand = wp_dropdown_categories( array(
'pro' => true,
'thepostid' => $post_id,
'show_option_none' => __( 'Select brand', 'dokan' ),
'hierarchical' => 1,
'hide_empty' => 0,
'name' => 'brand[]',
'id' => 'brand',
'taxonomy' => 'brand',
'title_li' => '',
'class' => 'product_tags dokan-form-control dokan-select2',
'exclude' => '',
'selected' => $selected,
'echo' => 0,


) );

echo str_replace( '<select', '<select data-placeholder="'.__( 'Select brand', 'dokan' ).'" single="single" ', $drop_down_brand );
// validate acf fields before save
add_action('dokan_process_product_meta',$drop_down_brand, $post, $post_id, 10 );

// save custom field data in product meta.
add_action( 'dokan_new_product_added', $drop_down_brand, $post, $post_id, 10, 2 );
add_action( 'dokan_product_updated', $drop_down_brand, $post, $post_id, 10, 2 );

add_action( 'dokan_product_edit_after_product_tags', $drop_down_brand, $post, $post_id );?> please can see or help me if i need another hook or something thanks for all