bigquery data transfer service for google ads

[Vigneshwaran]

Hi 
I am trying to setup/create a BigQuery data transfer service for google ads.
From the google documentation i know we can setup this in 2 ways.

1. using user account 

2. Service account.

1. using user account  to create a transfer using user account the documentation is really clear it has  step by step instruction, i just followed this link 

https://cloud.google.com/bigquery/docs/google-ads-transfer

in this approach while it is trying to transfer the data, the transfer job is getting failed with below error.

generic::permission_denied: Error while processing subtask: The caller does not have permission Raw error response from Google Ads API: { "error": { "code": 403, "message": "The caller does not have permission", "errors": [ { "message": "The caller does not have permission", "domain": "global", "reason": "forbidden", "debugInfo": "detail: "[ORIGINAL ERROR] generic::permission_denied: User doesn\'t have permission to access customer. Note: If you\'re accessing a client customer, the manager\'s customer id must be set in the \'login-customer-id\' header. See https://developers.google.com/google-

I know the reason for the failure, google trouble shouting  document also explain this.

i posted my question in stackoverflow.

https://stackoverflow.com/questions/77235203/google-ads-bigquery-data-transfer

here the conclusion is simple if i can't authorize my data transfer using different id(which is not used to create a transfer) the i can't go with approach. Because ,

As per my organization setup the id which is access to GCP is don't have access to google ads same way the id which has access to google ads doesn't access to GCP. 

is it not at all possible use different user to authorize google ads data transfer?

2. Service account.  For the data transfer setup using service accounts i can see only this document    https://cloud.google.com/bigquery/docs/use-service-accounts    it is not having step by step procedure as like other one(user account documentation).

which is basically missing the steps of how to ad service account to google ads.

i updated my existing data transfer's transfer owner as my service account, now i am looking for the steps to add my service account to google ads to access google ads accounts.

i can find only below link which explain how to add service account to google ads manager https://support.google.com/admanager/answer/6078734?hl=en   . do i really need to add my service account at ad manage level? is it not possible to add the service account to manager account(MCC) level?

Thanks,

Vicky...