When your SSL certificate expires, it becomes unavailable. You must purchase another one. After purchasing a new certificate, you need to re-bind the domain name and submit materials for review.
Once the review process is complete, a new certificate is issued. To replace the expired certificate, you must install the new SSL certificate on your server.
Note Purchase the replacement certificate three to ten working days before certificate
expiration so that the new certificate can be reviewed before the existing certificate
expires.
For more information, see New purchase upon expiration.