Hi,
Thank you for reaching out to us. You should be able to get customer data using
this example via the API. I also took a look at your account 8975708356 and see that it's a production account. If you've had access to the API (AdWords) before, you should be able to use the same developer token to access the API. However, if your only developer token is set at test level access and you do not currently have any developer token with basic/standard level access and need to access production level accounts, you will need to apply for basic level access
here. If you're still having issues, could you please provide me with your REST Request and Response logs so that I may further investigate this issue? For privacy concerns, you may reply using the "Reply privately to the author" button.
Thank you,
Bryan, Google Ads API Team

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