This solution worked for me:
add this code in your /public/www/wp-content/themes/<theme>/functions.php
add_filter ( 'woocommerce_product_thumbnails_columns', 'zz_thumb_cols' );
function zz_thumb_cols() {
return 8; //Change the 8 to reflect how many columns you need
}
source:http://chromeorange.co.uk/woocommerce-set-number-of-thumbnail-columns/
I hope it helps
Best Regards
Filipe