429 RESOURCE_EXHAUSTED "prepayment credits are depleted" despite active billing and $0 spent

Project ID: gen-lang-client-05779752..
Billing account ID: 01C1CE-8680D4-5AE8..

I upgraded from free trial to a full paid account today (confirmed via email
“Gracias por actualizar a una cuenta pagada”). The one-time prepayment of
COP 100,000 was confirmed received (payment confirmation email received).
Monthly spend limit is set to COP 60,000 with COP 0.00 used.

Every call to generateContent using gemini-2.5-flash-image (Nano Banana)
returns:

429 RESOURCE_EXHAUSTED: “Your prepayment credits are depleted.”

This happens even on text-only models like gemini-flash-lite-latest, which
worked fine before I enabled billing today.

models.list() works fine and returns all models correctly.

This matches the billing sync issue reported by other developers recently.
Could you please perform a manual billing sync on this project?