Hello Tanya,
To facilitate the exchange of possibly private information and attract the attention of Developers to you issue, you are encouraged to open an issue in the
public issue tracker. This issue should have the same content as your posting here, with more details and the result of the command indicated below.
What is the result of running the gcloud beta app domain-mappings list command?
You are right: in just minutes, a certificate should be in place and serving client requests.