The most current version of Start8 works with Windows 8.1 update 1. You can install it now and when you update to 8.1 you should be good to go.
Serials and download links can be accessed by logging in with a Stardock account at https://store.stardock.com/myaccount/products or installing through Object Desktop Manager if you're a subscriber (available here http://www.stardock.com/products/odnt ).
**** If this does not resolve the issue, please contact support: Submit a ticket ****