Hi,
You are correct that the usual cause of this error is you are passing an incorrect/non-existing client customer ID on the request header of your transaction.
So that I can further check the issue, could you provide the complete SOAP request and response logs together with the
customer ID via
Reply privately to author option? You can enable the SOAP logging by referring to this
section for the Python client library.
Regards,
Ejay
Google Ads API Team

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