When you go try to sign up with Cobiro, you can see the options for "Advertisers" and "Agencies".
The "Advertisers" solution allows all users to connect only one Google Ads account (previously known as Google AdWords) to Cobiro. If you have a manager account containing multiple Google Ads accounts, you need to select one sub-account to connect to Cobiro.
You can connect an unlimited number of Google Ads accounts to Cobiro but each of your accounts needs to be associated with one separate Cobiro account.
The "Agencies" solution is made for marketing agencies managing numerous Google Ads accounts of their clients. By choosing this solution, our CSS partner Comlyn will connect you to a multi-client account (MCA) in its CSS approved Merchant Center. From there you can add your clients' Google Ads accounts and provide them with all of the CSS Partner program benefits.