Hi Amber,
Yes, if the email you are authenticated as is not the email you used to create your OAuth2 credentials, you will receive a permission error. I suggest using the email connected to your OAuth2 credentials or creating new credentials with the email address you are currently using. Additionally, you will also need to ensure that the email address you are using is added as a user to your account. You can do this by going into the UI -> Tools & Settings -> Setup -> Account access and security. If you continue to experience issues, please provide your account's CID, complete detailed logs of the request and response, as well as the email address you are using to authenticate the API call so that I can take a closer look.
Regards,
Danica, Google Ads API Team

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