Programmatically create certificate for change notifications

Question

https://learn.microsoft.com/en-us/graph/webhooks-with-resource-data?tabs=csharp#managing-encryption-keys

The site above demonstrates how to connect to MS Graph for change notifications. However, the documentation is lacking on ways to create a valid certificate. We are trying to create a certificate programmatically, but no matter how we do it, MS Graph will not except it. We are currently using a static cert from a different vendor. Could you I get some sample code snippets (C#) showing how to create an acceptable cert? or be directed to docs demonstrating this.

Thank You!