I recently purchased a Dyson on a TSV. I have tried to register the warranty online for the machine and it tells me I am not entering a valid serial number. I am entering the number that is off the paper you would mail in if you choose to register it by mail. This number matches with what is on the machine as well. It has numbers and letters in it which makes me curious as to maybe that's why it is not identifying correctly.. ? Has anybody else had this problem before??