Issue
When using type of connection 'SharePoint Online : List & Library' and 'SharePoint Online: Site Collection Administration', this error might occurs:
Unauthorized request for connection <connection name>
Unauthorized request for connection <connection name>
Resolution
Configure the connection manager 'SharePoint Online Tenant URL' without -Admin as the URL.
Incorrect value: https://tenantname-Admin.sharepoint.com
Correct value: https://tenantname.sharepoint.com
Incorrect value: https://tenantname-Admin.sharepoint.com
Correct value: https://tenantname.sharepoint.com