Duplicate Sku

Hi

I am trying to upload products via csv. However getting an error saying they are duplicate sku;s.

I read a workaround where it involved adding a line to functions.php

add_filter( ‘wc_product_has_unique_sku’, ‘__return_false’, PHP_INT_MAX );

This is the result and where i placed it

function flozen_setup() {
        load_theme_textdomain('flozen-theme', FLOZEN_THEME_PATH . '/languages');
        add_theme_support('woocommerce');
        add_theme_support('automatic-feed-links');
        add_filter( 'wc_product_has_unique_sku', '__return_false', PHP_INT_MAX );
        add_theme_support('post-thumbnails');
        add_theme_support('title-tag');
        add_theme_support('custom-background');
        add_theme_support('custom-header');
        add_filter( 'wc_product_has_unique_sku', '__return_false' );

Issue is it still will not accept duplicate skus