Let me try again...
I have my Windows 8.1 upgraded from 8. It's open in normal oobe.
Then I'm ready to start following your instructions to run sysprep on an upgraded system.
Next, I run:
cmd (admin mode)
As expected, it displays an error message like the one you have in the post. And the reason it's because I have an upgraded system.
C:\Windows\System32\Sysprep>sysprep.exe /audit /reboot
The next thing you ask to do is to reboot and return to audit mode with sysprep dialog open in the desktop. But that's the problem: if I reboot it doesn't enter in audit mode and I don't know how to do it. By trying the command above it issues an error.
I saw something related to configure the Microsoft-Windows-Deployment | Reseal | Mode setting to audit
But I don't know how to do it.
I hope I was clear now.
Thanks for your patience.