Project consistently fails with 403 CONSUMER_INVALID error on Firestore API calls

Hello Google Cloud Community,

I am developing an application and have encountered a critical, persistent issue that has completely blocked my progress.

Project Information:

  • Project ID: (PII Removed by Staff)

  • Billing Account ID: (PII Removed by Staff)

The Issue:
All API calls from a Python script to the Firestore service are consistently failing with the error: “403 Permission denied on resource project (PII Removed by Staff). [reason: “CONSUMER_INVALID”]”.

Troubleshooting Steps Already Taken:
I have exhaustively performed all standard troubleshooting procedures without success. These steps include:

  1. Creating a completely new, clean project (PII Removed by Staff).

  2. Verifying that the project is correctly linked to an active and healthy Billing Account.

  3. Enabling all necessary APIs (Firestore, Datastore, Gemini).

  4. Creating a new Service Account (executor “at”…) and granting it the “Editor” role.

  5. Generating and correctly configuring a new JSON key for this Service Account.

  6. Using a minimal, isolated Python test script to confirm the issue is not with my application’s code.

  7. I have also confirmed that manual data creation within the Firestore web console works successfully, which proves the issue is specific to the API access path.

The persistence of the CONSUMER_INVALID error, despite all correct front-end configurations, strongly suggests a backend state inconsistency between my Google Account, my billing account, and the GCP project.

As I do not have a paid support plan, I am unable to create a technical support case and am turning to the community for help.

Has anyone encountered a similar issue? Are there any other suggested steps to resolve this blocking consumer validation error?

Thank you very much for any assistance you can provide.