5) Apologies, I did not mean 1200×800. I mistyped that. I meant a greater dimension such as 1024×1024 as an example.
If I use the supplied image, it uploads and displays correctly for me locally:
On your installation, WooCommerce is outputting the generated WooCommerce image sizes:
Your site:
VS Mine, notice the 540×540 prefixed to the end of the image URL:
I do wonder if your server is not generating the sizes, upon looking at your System Status, I notice you are running a version of PHP that Woo does not support: https://monkind.com/wp-admin/admin.php?page=wc-status
If you can contact your host, ask them to upgrade your PHP/MySQL versions to the latest. Once complete, rebuild the images once more.
Thanks.