CPT with URL rewrite showing as 404

Step 1: Flush Rewrite Rules

Manually: Visit Settings > Permalinks and click “Save Changes”.

Programmatically (temporarily):

function my_custom_flush_rewrite_rules() {
    flush_rewrite_rules();
}
add_action( 'init', 'my_custom_flush_rewrite_rules' );

Step 2: Add Custom Rewrite Rules

function custom_rewrite_rules() {
    add_rewrite_rule(
        '^products/([^/]+)/([^/]+)/?$',
        'index.php?post_type=product&product_category=$matches[1]&name=$matches[2]',
        'top'
    );
}
add_action( 'init', 'custom_rewrite_rules' );

Step 3: Modify post_type_link Filter

function add_custom_rewrite_rule( $post_link, $post, $leavename ) {
    if ( $post->post_type === 'product' ) {
        $terms = wp_get_object_terms( $post->ID, 'product_category' );
        if ( !is_wp_error( $terms ) && !empty( $terms ) && is_object( $terms[0] ) ) {
            return str_replace( '%product_category%', $terms[0]->slug, $post_link );
        }
    }
    return $post_link;
}
add_filter( 'post_type_link', 'add_custom_rewrite_rule', 10, 3 );

Step 4: Register CPT and Taxonomy

Custom Post Type:

function register_custom_product_post_type() {
    register_post_type( 'product', array(
        'labels' => array(
            'name' => __( 'Products' ),
            'singular_name' => __( 'Product' )
        ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array( 'slug' => 'products/%product_category%', 'with_front' => false ),
        'supports' => array( 'title', 'editor', 'thumbnail' )
    ));
}
add_action( 'init', 'register_custom_product_post_type' );

Taxonomy:

function register_product_category_taxonomy() {
    register_taxonomy( 'product_category', 'product', array(
        'labels' => array(
            'name' => __( 'Product Categories' ),
            'singular_name' => __( 'Product Category' )
        ),
        'hierarchical' => true,
        'rewrite' => array( 'slug' => 'products' ),
    ));
}
add_action( 'init', 'register_product_category_taxonomy' );