Opened the CloudSOC Tenant > Users (upper right corner) > +New > User: Entered User Name, Email and other required fields and then clicked Save; found the process failed with error popup.
"User is already active in ' sample tenant name' account".
The same email cannot be active in two separate tenants becasue it would cause conflicts with securlet monitoring and activation (among other potential problems).
There are three options to fix the error.