In an effort to continue to push WooCommerce forward, the latest version of Woo now requires a website to be running on PHP 7.0 or later. Sites running on earlier versions of PHP will not be able to upgrade.
If you’re having trouble upgrading PHP, here’s a handy article by WordPress.org to help: Get a faster, more secure website: update your PHP today
If you’re still having trouble, start a chat with us and we’ll see how we can help.