This document is for anyone who has received an email from PayPal with the subject : IMMEDIATE ATTENTION REQUIRED: PayPal service upgrades
PayPal is upgrading the certificate for www.paypal.com to SHA-256. This endpoint is also used by merchants using the Instant Payment Notification (IPN) product.
The WooCommerce PayPal Standard Gateway itself requires no changes. You should however check that your hosting provider supports the new certificates.
In the event that your host does not support SHA-256, customers will still be able to make payments, but the PayPal IPN will not be able to update orders from ‘pending’ to ‘processing’ without manual intervention.
The PayPal Sandbox has already been updated to SHA-256. You can test your own site by placing an order using the PayPal Sandbox or you can use this tool which will confirm if PayPal IPN will continue to work on your site after PayPal makes the change on the Live environment.
To use the tool just click the “Download ZIP” button in the bottom right corner
and install as you would any other plugin. Once installed just click the link
and you will see either a Success or a Fail message
If the check fails you will need to contact your host about this, this is not a WooCommerce or WordPress issue.