Manual Billing Sync Request: Prepayment required despite active Cloud Billing account

Billing Account ID: 0161F1-DBF68F-4F883A
Project Name: Default Gemini Project (gen-lang-client-0464252366)

Issue Description:
My Google Cloud Billing account is active, verified, and linked to my project. However, Google AI Studio displays: “No prepayment method set up for this billing account. Prepay is required for this billing account.”

When I click the “Set up prepay” button, the popup modal opens completely blank/black and fails to load the payment interface (tested in standard, Incognito, and alternate browsers).

Please manually synchronise the prepayment state for this billing account and project.

I click setup prepay; a popup shows up with an email address and country. I press agree and continue, and then nothing happens.