Please note that the email address of the driver in the invitation email does not need to match the email address of the Kia account of the driver.
That means e.g. if drivers are invited through their company email, they can use their private email to register with a Kia account.
Unfortunately, the email address of the Kia Account cannot be seen in the portal.
However, in the Fleet Portal you will be able to see if the driver is successfully registered.