I have MC 19 in my PC and MC 20 in my laptop. I tried to upgrade the PC version with the restore key from MC 20 and I am told that it is not valid for upgrade and that I need to purchase an upgrade. I already bought the 19 (PC) and the 20 versions (laptop) at full price, so I do not know why I have to pay to upgrade version 19 in the PC. Can anyone help me?