Hello Denise,
Thanks for writing in!
1.) It has come to my attention that you are using Pro 1.1.0 which is outdated. Pro 2.3.6 is now available in automatic updates! This release contains fixes for several issues so be sure to check out the changelog (https://theme.co/changelog/). Please do update to the latest version and this should resolve your issue. After doing the updates, always remember to clear all caches when updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
2.) The product thumbnail feature is the new WooCommerce product gallery slider. If you want to display the old way of display the product images, we would highly to suggest that you use a child theme because what you are trying to accomplish requires a template customization, . This allows you to make code changes that won’t be overwritten when an X update is released. After the child theme is set up, please add the following code in your child theme’s functions.php file
// Remove product gallery slider and gallery zoom
// =============================================================================
add_action( 'after_setup_theme', 'remove_woo_three_support', 11 );
function remove_woo_three_support() {
remove_theme_support( 'wc-product-gallery-zoom' );
remove_theme_support( 'wc-product-gallery-slider' );
}
// =============================================================================
Please let us know how it goes.