With Mailchimp, it is not possible to fetch data from multiple business accounts with the same email address.
Workaround
To fix this, please assign unique email addresses for each business account. Therefore, please log in with a different email address for each business account.
How?
For Google Sheets
When you add a new user account in the sidebar, as below, please select a different email address for each user. To authenticate Mailchimp in Google Sheets, please see this guide.
For Data Studio
When you add a new user account, as below, please select a different email address for each user. To re-authenticate Mailchimp in Data Studio, please see this guide.
