Google cloud "API not enabled" problem

Hi,

I am following the paticle’s google cloud tutorial example (and had some issue):
https://docs.particle.io/tutorials/topics/google-cloud-platform/#storing-data-in-a-datastore-database
When i am at the end of the example, the tutorial told me to go to “https://github.com/spark/google-cloud-datastore-tutorial” and when I finally reached the last thing of the tutorial, after I entered “node tutorial.js” in my Windows cmd window, it kept telling me:
"Authenticating with Google Cloud…
Authentication successful!
events.js:141
throw er; // Unhandled ‘error’ event
^

Error: Google Cloud Pub/Sub API has not been used in project crested-century-145518 before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/pubsub.googleapis.com/overview?project=crested-century-145518 then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry.
at C:\Users\Ti\Documents\Websites\google-cloud-datastore-tutorial\node_modules\google-cloud\node_modules@google-cloud\pubsub\node_modules@google-cloud\common\node_modules\grpc\src\node\src\client.js:417:17"

then as I went to my google cloud page to check, I found that my Pub/Sub API is actually en-abled. Do anyone know how to fix it? (if you need more information, I would love to provide.) I really hope it to be fixed soon!

Thanks,

Tianyu Guo (Ti)