Since Header Bidding advertisers participate in the Google Ad Manager (GAM) price priority auction, you need to connect your GAM account to the Header Bidding platform.
During the first log into your account, you will see the following pop-up window:
1. In order to automatically create entities that are necessary for the work of Header Bidding technology, you need to enable API access in your GAM account (Admin --> Global Settings).
2. By clicking on the “Connect” button, you will be redirected to the Google account log in page. After selecting an account, you will see the list of permissions that should be granted to HBMP. Make sure you link the correct account with the right permissions.