Google Ads API – UNIMPLEMENTED (501) on customers:listAccessibleCustomers

[정예은]

Hello Google Ads API team,

I am currently using Developer Token: 8GucfeV9Q5U6zsq_J11cmw  
MCC Account ID: 486-111-9693  
API Contact Email: jjung...@gmail.com

We have followed all standard OAuth2 steps:
- Obtained refresh_token  
- Generated access_token  
- Made a GET request to https://googleads.googleapis.com/v18/customers:listAccessibleCustomers  
  with required headers (Authorization Bearer ..., developer-token: 8GucfeV9Q5U6zsq_J11cmw)  
- Received HTTP 501 UNIMPLEMENTED response with message:
  "Operation is not implemented, or supported, or enabled."

Other accounts in our organization using similar setup are working fine.  
We suspect that for this particular developer token / MCC combination, the API capability is not yet enabled.

We have already submitted the Standard Access application for Google Ads API from our account, but the token still cannot access the most basic endpoint.

Could you please check the status of our developer token and enable the “customers:listAccessibleCustomers” endpoint for us?  
If you need further logs or additional information, we will gladly provide them.

Thank you for your assistance.

Best regards,  
jung yeeun
Company: [qgenic]  
Website: https://qqq7856.cafe24.com/  

[Google Ads API Forum Advisor]

Hi Jung,

Thank you for reaching out to the Google Ads API support team.

I understand you've encountered a "501 UNIMPLEMENTED" error while making the ListAccessibleCustomers request via the Google Ads API. I've verified your account 486-111-9693 and confirmed that the developer token has the basic access. It appears the issue is not related to the developer token.  

 

Also, I could see that you are still using the 'v18' of the Google Ads API which is already deprecated. I would recommend migrating to the latest version v22, please follow this guide to upgrade to the latest version. 

If the issue still persists, to investigate this further from our end, please provide the following details:

 

• The Customer ID used for making the API request.
• Complete API logs (request and response with request-id and request header) generated at your end.

If you are using a client library and haven't enabled the logging yet, I would request you to enable logging for the specific client library that you are using. You can refer to the guides Java, .Net, PHP, Python, Ruby or Perl to enable logging at your end. For REST interface requests, you can enable logging via the curl command by using the -i flag. 

 

If you need assistance on the standard access application that you have submitted, I would recommend you reach out to the Google Ads API Compliance team, as they are better equipped to address your concerns. Please note that concerns related to the developer token access requests are out of scope for the Google Ads API support team as our team can only assist with the technical queries or concerns related to the Google Ads API. 

 

You can send the details via Reply privately to the author option, or direct private reply to this email.

 

Thanks,
 

Google Ads API Team

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[2025-10-31 07:42:06Z GMT] This message is in relation to case "ref:!00D1U01174p.!500Ht01vSKx8:ref" (ADR-00338071)