I wasted several hours this week going around in the exact same circles. We have a billing account, but kept hitting a gemini quota. Fine. But then on the quota page, every quota said 0% usage. And our bill was like $5. Some docs said check AI studio, but then the "import project from google cloud to AI studio" button kept silently failing. This was a requests per minute quota, which was set at 15 (not a whole lot...) but wouldn't reset for 24 hours. So then I kept making new projects so I could keep testing this thing I'm building, until eventually I ran out.
The only way we could get it resolved was to (somehow) get a real human at google on the phone because we're in some startup program or something and have some connection there. Then he put in a manual request to bump our quota up.
Google cloud is the most kafkaesque insane system I've ever had the misfortune of dealing with. Every time I use it I can tell the org chart is leaking.