All App Store Connect data sources fail with "403 Access Denied"
What you see: Every App Store Connect data source suddenly fails with a 403 Access Denied error. Reconnecting with brand-new API keys fails too.
Why it happens: Apple blocks all API access when a required agreement on your App Store Connect account is missing or has expired. Apple reports this as REQUIRED_AGREEMENTS_MISSING_OR_EXPIRED.
What to do:
Ask the Account Holder of your App Store Connect account to go to App Store Connect > Business and sign every agreement that isn't Active.
Once the agreements are active, your existing API key works again. If you didn't revoke the old key, you may not need to reconnect.
Check that the key you use is a Team key (not an Individual key), with a role that has access to Analytics Reports.