How to renew certificate, Cesium Certificate Developer?

Few days ago, I received an email which said that my certificate would expire.
That mail contains the button, “Send an mail to Cesium Inc!” so I sent my request to renew my certificate.
But I did not receive any response.
What do I have to do?
Thank you!

Certificate expiration notices go out a month before they are due from a third party certification system. You should receive an email shortly with instructions on how to re-certify. Feel free to reach out to certifications@cesium.com with questions.

Thank you. I have just received the response.