My EVO drive is listed along with other products with active warranties. Try using the Members app when entering the serial.
I found a solution for me. I have MacOS, and I looked up the serial number through the OS under system report to register both of my SSD. The S/N on the box is incomplete and the OS recognizes the entire S/N.
So try to look up the S/N inside "hardware" whether on Windows or Mac and type that in. This might help you.
Also use the "Model Code," not the Model # on the box if you are having issues with that
Using the Model code worked for one of my 860 EVOs but the a second one won't register because of serial number. The Samsung Magician software showed the same number as on the box except with a "F" at the end. It won't register with either.