I upgraded from Windows 8.1 Pro x64 to Windows 10 Pro x64 (build 10240) and was not asked for a key. My 8.1 key was a retail key I bought from Microsoft. Are you definately going to the same version, and how are you licenced - i.e, key bought from Microsoft?
Possibly although I can't see how this would be a massive reason why, what are you using to upgrade, are you using one of the ESD's converted to ISO? I would make sure you are using the same upgrade path - i.e, if your current Windows 8.1 is x64 PRO, make sure you are using the Windows 10 x64 PRO ESD to upgrade with. It wouldn't hurt to be fully patched I guess...
I have this ESD converted to ISO 10240.16384.150709-1700.th1_CLIENTPRO_RET_x86fre_it-it_A314F2F3CCF9E0E14BCB05324BAB43F476EABA7E.esd There is a required update list ?
@ a0a0 - You have no option to click "Skip" when prompted for a key? You are upgrading by running setup.exe from burned disc/USB stick?
Probably not new news but you absolutely have to be connected to the internet to get reactivated after a clean install but you do NOT need to be using a msa, local accounts work fine. I just ran another test to verify all of that.
Don did you see this post where Atari had tested if he could restore tokens.dat to a clean install of a previously activated systeem. SuperFly answered here. But as you say, for the moment it seems there is no way to successfully backup/restore activation without connecting. Edit: Sorry to repeat this but those of you requesting ESD's at the moment. It's worth bookmarking xinso's post a few pages back and keep checking. He's updating it every few minutes with links. The MS links don't last long so check frequently. Also check antonio8909's posts over recent pages.