Hi Guys, So I had this exact issue, went through the forum and didn't find a solution. However, just before giving up I noticed that my Samsung Account session had expired. So I decided to log in and after doing so I thought to myself to try the SecureFolder once more. It worked. So basically I'm suggesting that persons try/ensure logging into their Samsung accounts before setting up the secure folder. Hope this helps.
Thanks for reaching out. This forum is for support of US products and customers. As your product is a non-US model and support for these models is very limited, please seek a support team for your area. You can do so by using this link: http://www.samsung.com/visitcountry
"once a phone has been rooted there is no way to remove or undo it."
This is not true. If you did not unlock the bootloader, you can simply install a stock image to remove it.
"A superuser account on Android is similar to an administrator account."
A superuser account is identical to the root account on Ubuntu, since Android is based on Linux.
"The result of that action is that you void your warranty, and possibly break your phone permanently."
Rooting also means that you are also 90% more likely to be able to fix your device without data loss.
"You are also now in charge of keeping track of your own Android maintenance and any system updates are now your responsibility."
Again, this only applies if you unlocked the bootloader. System root requires that you disable updates to avoid them being installed and removing root from the device. There would be no concern about root being removed if you were no longer able to update normally.
As a Samsung employee, I understand that it is your job to deter people from rooting. That should not mean you lie to the customer. Rooting typically disables the "secure" aspects of the device because Knox is designed not to function on rooted devices. It is no different than any game that says you are running an illegal program because of a certain app that is installed. It is a manufacturer preference.
To restore your device (assuming you do not have an unlocked bootloader), you could try using an app like SuperSU to remove root. Make a backup of your phone, perform the removal, and then install a stock firmware (if updating does not work or the secure functionality is not already restored).