Sandbox reports always return Success with a null ReportDownloadUrl; account shows "primary payment method needed"

In the Microsoft Advertising sandbox (REST API v13, Reporting service), SubmitGenerateReport succeeds for all nine report types we request, and PollGenerateReport returns Success with a null ReportDownloadUrl every time. This has happened on every run since 12 Oct 2026, including runs on the UTC day new keywords were created, which the sandbox guide says should generate test data.

Sign-in: personal Microsoft account (outlook.com), as the sandbox requires

Entities: one Search campaign, two ad groups, ads and keywords (latest keyword created 14 Oct 2026), all Enabled / Eligible

The account shows "You need a primary payment method before your ads will run", its setup stops at "Complete setup", and "Add card" only reloads the page. The sandbox guide says payment methods are not supported in sandbox.

Questions:

1. Is this payment-method state the reason no sandbox test data is generated?
2. If so, how should a sandbox account complete setup?
3. Would an account created through "Go Live" with "Skip payment information" behave differently?

Thanks.