Hi Amit,
Thank you for reaching out. I tried looking into the account associated with the shared email address: am...@theagency.com and found that the account is in draft state. Could you please complete the setup from the Google Ads UI and then apply for the developer token and OAuth credentials using the signup guide? Please give this a try and let me know if you are facing any issues.
Regards,
Nikisha Patel, Google Ads API Team