it seems plugin of jcloud have hardcoded zones in the code and it doesn't fetching directly from the api. So when the GCP changed, or one of the datacenter went down, JCloud won't work anymore, because that zone can be found anymore. Here is the trace message:
And when I listing via CLI of gcloud:
There is no "d" zone either. So our CI builds can't work right now even we don't using that region of us-central1.