Hi David,
This account doesn't have any Campaigns, AdGroup, Ad and performance stats like Costs, Clicks, so the report is null. Could you please try downloading the report after adding these missing entities (Campaigns, Ads). If you are still facing an issue, please share the report definition so that I can troubleshoot the issue. You can use 'Reply privately to author' option while responding.
Thanks,
Milind, AdWords API Team