Hello Om,
Thank you for writing to us. The error TWO_STEP_VERIFICATION_NOT_ENROLLED occurs if the client account is enrolled in 2-Step Verification and the accounts accessing it are not. Please refer to this blog post for more details and information. Could you please confirm if you are added as a user on the Google Ads account? Or is your API call authorized by a user who has access to the target account? If it is the second case, that user who authorized the API call and generated the authorization code should also have their Google accounts enrolled in 2-Step Verification. If you are directly a user on the account, and have already enrolled for 2-Step verification, could you confirm the Google Ads account and the email address against which you are making the API call?
P.S. Please use Reply privately to author option while sharing the details.
Regards,
Nikisha Patel, Google Ads API Team