Cannot install CALs on Windows Server 2016 (CALs that were included with the purchase)

Good day, I had purchased a Windows Server 2016 Standard license in October, and the one I purchased is with the following title:

Windows Server 2016 Standard 10-Client Access License (English)

I have activated the server successfully, but when I try adding the CALs in RD licensing manager, I get an error that the license code is not recognized. I figure that it's looking for a CAL purchase license code. But according to the title I thought I had purchased Windows Server including 10 CALs. Am I wrong? Or how do I go about licensing the CALs?

Thank you very much in advance for any help. I've spent hours online looking for a solution and even with MS support on the phone, but I am not getting any helpful information.

Kind regards, Timmy.