Hello Andrei,
Could you please confirm whether the login user has access to the project and the OAuth credentials are created by the same user? I see that some of the users faced this error when they used proxy or any extension to the browser that is blocking the part of the URL. If the problem persists, I recommend you to create a new set of credentials using this
OAuth guide.
Regards,
Sai Teja, Google Ads API Team

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