WPDB::prepare incorrect. The query argument of wpdb::prepare() must have a placeholder

Question

having this error do you know what is wrong with my code?

Notice: wpdb::prepare was called incorrectly. The query argument of wpdb::prepare() must have a placeholder.

Notice: Undefined index: key - the key has a value

    global $wpdb;
    $id = '';
    $post_id = get_the_id();
    $count = 0;
    if(is_array(LPListingsField::$field_groups)){
        foreach(LPListingsField::$field_groups as $key => $args){
            $fields = isset($args['fields']) ? $args['fields'] : [];
            foreach($fields as $_key){
                $field_value = isset($_POST[$_key['key']]) ? $_POST[$_key['key']] : [];
                $field_key = isset($_key['key']) ? $_key['key'] : [];

                if($update){
                    $wpdb->update($wpdb->prefix."lp_listings_meta", array(
                        $field_key => $field_value,
                    ),
                    array( 'post_id' => $post_id ),
                    );
                }else{
                    $wpdb->insert($wpdb->prefix."lp_listings_meta", array(
                        $field_key => $field_value,
                    ),
                    array( str_repeat("%s,",$count)),
                    );
                }
                $count++;
            }
        }
    }