If you are not getting e-mails then it sounds like your ISP or your e-mail client is deleting them. I recommend checking your junk folder.
If you purchased Start8 via the Stardock store then you should have created an account (or used your current one), in which case you should be able to download Start8 from the MyDownloads section or the store, or by using the trial and using the unlock option and using your account details.
Having checked the system requirements for Galactic Civilizations II: Ultimate Edition on Steam I notice it says :
Operating system: Windows® XP SP3 / Vista™ SP2 / Windows® 7
It may be this has not been updated since 8 came out, or it may well be those games do not work on Windows 8. They were certainly designed long before Windows 8 even existed.