In my experience GPU persistent instances often simply don't boot up on GCP due to lack of available GPUs. One reason I didn't choose GCP at my last company.
I think it was us-east1 or us-east4. Had issues getting TPUs as well in us-central1. I know someone at a larger tech company who was told to only run certain workflows in a specific niche European region as that's the only one that had any A100 GPUs most of the time.