From the info provided, I understand you are attempting to change the Billing account associated with your GCP Project following the steps described here[1]. The error you got indicates that the GCP team were unable to verify billing instrument ownership using the documents you’ve submitted.
I recommend that you resubmit the documents through our online verification form [2] for your specific Billing Account including proof of ownership of Payment Method.
Also, please be advised that the documents for verification needs to meet these requirements:
- ensure that only the last 4 digits of the Card that is showing.
- Please submit an image of the statement for the Credit card
- make sure that the name on the card and the expiry is fully visible on the image.
- provide any Government Issued ID that will serve as Proof of Ownership of the Payment Instrument on file.
Once done, Google Trust & Safety Team will further check your account. Verification generally takes less than 4 hours, but may take longer in some cases.
Better still, to help review this issue, I suggest you contact the Google Cloud Platform Billing support via this link[3] or you should open an issue link via the GCP Issue tracker[4]. A support engineer will be able to assist you better by reviewing your setup.