AWS Bedrock Anthropic models returning AccessDeniedException despite IAM policy configuration and submitting use case details

Hello.

I'm experiencing the same 403 error on my personal AWS account.
For new models, usage may not be permitted by default for AWS accounts with low usage levels until demand stabilizes.
It wasn't with GPT, but I once resolved a similar error by contacting AWS Support regarding Claude.
It would be best to contact AWS support.

Incidentally, I came across a Japanese blog that recommends opening a case under "Account and billing".
https://qiita.com/Maki-HamarukiLab/items/7bff94a6b2d37b6d091e

Hey — beyond IAM and the FTU form, there are actually 4 blockers that all have to pass simultaneously: (1) IAM needs aws-marketplace:Subscribe/Unsubscribe/ViewSubscriptions in addition to bedrock:InvokeModel, (2) the FTU form must be submitted at the org management account level (not just a child account), (3) no SCP blocking Bedrock in your region, and (4) a valid payment method on the account — if you're on an Indian AISPL account, card alone won't work, you need invoice billing enabled via a support ticket. Enable Bedrock Model Invocation Logging (Bedrock Console → Settings, 5 min, free) — it'll tell you exactly which one is failing. Happy to help diagnose further if needed.

Wrote up the full diagnostic (copy-paste IAM policy, the exact FTU API call, SCP steps, a validation script) as a $75 report if useful: https://cloudnestle.com/deck/JRkGPI65L8MqFw1V.html