This exact thing happened to me when I ran https://www.fatherly.com/ circa 2017. Google just shut down our account without notice. We were spending like $10k/month. It also locked us out of our premium support account, so we couldn't even get anyone there to notice that they'd locked us out.

After about 8 hours, a random Google support tech said it was because we were mining bitcoin, which was laughably untrue. We had CPU usage graphs and logs for the whole time and there was no spike. At around 12 hours, they turned it back on, said it was "misconfiguration of our abuse detection" and gave us like $100 in credit.

Absurd. Say what you will about AWS, they would never do that to a customer without a rep reaching out to you first. I have not trusted GCP since.