The error:
Download failed. server certificate verification failed. CAfile: [Path_to_Certificate] CRLfile: none
The Problem
Your website doesn’t recognize the SSL certificate on yoast.com.
The Solution
Please contact your web host and ask them to add our certificate to the list of trusted ones. Once the certificate is trusted, you will again have access to automatic updates. In the meantime, please manually update your plugin using the steps found here: How can I manually update my premium plugin?