Good evening Mary and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
First off, kudos on finding the culprit.
For some reason, it looks like with your theme or theme settings, the standard CSS from WooCommerce is not kicking in on that button or rather is using white as a border color.
Try adding the following CSS rule to your style.css file or in your Custom CSS metabox:
.page-wrapper .woocommerce a.button {border: 1px #d3ced2 solid !important;}
Let me know how that goes.
Best regards,
Geoff B.