So in order for your Komplete 10 to work you already should have a previous Komplete version registered on your NI account (Not sure exactly which versions qualify but it will probably be at least Komplete 8 & 9 and possibly older versions too), if you dont own (or have registered on your NI account) any previous version the update will not work and you will get that error.
#NATIVE INSTRUMENTS KOMPLETE 10 PRODUCT KEY SERIAL NUMBER#
The UPDATE serial number is to update your Komplete from a previous version you already own (and as such costs a lot less to purchase than buying a brand new full version), so if you have bought the UPDATE version you must already own and have registered on your account a previous KOMPLETE version (e.g KOMPLETE 9 etc.) Native Instruments Educational/ Student Discount: 50 off Reaktor 6 only.
If you bought the "UPDATE" that you mention, in order for the serial number to work you must already have a suitable "base product" on your account otherwise it will not work and you will get that error. If you do not already have any products from Native Instruments or even a Native Instrument user account and wish to buy and use Komplete 10 you need to buy the "full version" this works and can be installed on its own.