After having the same issue as the OP in this question, I was advised by a Google Billing Support Agent to delete the buckets created by the CloudBuild process initiated by the deployment of my Firebase Functions.
However, I now receive the following error when I attempt a deployment (function names changed):
⚠ functions[function1(us-central1)]: Deployment error.
Build failed: could not resolve storage source: googleapi: Error 404: Not Found, notFound
⚠ functions[function2(us-central1)]: Deployment error.
Build failed: could not resolve storage source: googleapi: Error 404: Not Found, notFound
⚠ functions[function3(us-central1)]: Deployment error.
I don't know the name of the original bucket so am unable to recreate it. I've tried reaching out to support again but they won't help as it's no longer a billing issue.
Is there a way I can get Functions to recreate the bucket so I can resume deployments?