Hi Zhongjie,
Thank you for reaching out. If you navigate on the customer resource page to the question “Is customer specified in the FROM clause of your query?” and select “Yes, it is”, then you will notice that the option for geo_target_region is gone. This is because when you specify customer in the FROM clause, some metrics and segments cannot be used. To fix this issue, you could query on the geographic_view resource or user_location_view resource to fetch the account consumption group by country. Please let me know if you have any further concerns.
Thanks and regards,
Xiaoming, Google Ads API Team