For those, like me, very frustrated by the not working PIN sign-up:
"From Somak Bhattacharyya, Program Manager for the Windows Team:
If you installed Windows 10 Technical Preview build 9926, you might have run into one or more of the following issues:
1. The PIN you set in a previous build was not preserved.
2. You are able to use the PIN to sign in, but you can’t change it in PC settings.
3. PIN doesn’t show up as a sign in option on the logon screen, even after creating it in PC settings. (This happens if you’re using a Microsoft account.)
4. When signing in with an Active Directory account, you see an “Object not found” error when you try to sign in using a PIN.
We apologize for these issues. Windows Insiders, like you, are helping us to build a new, truly great Windows. Unfortunately, the journey can be a little bumpy and you probably want to know what’s going on.
Until Windows 8.1, the PIN was a simple 4-digit substitution for your password. With Windows 10, we are building an entire infrastructure around PIN to keep your device and your services safer and more secure, while maintaining the simplicity of being able to sign in with a PIN. In the process of building this new infrastructure, we had to break some existing scaffolding. But not to worry, we’re working hard on this and will get the pieces put back together again soon. You’ll be able to enjoy the convenience of a PIN again in a flight in the near future. In the meantime, please use your password to sign in.
We understand how inconvenient this is, and we assure you of a speedy resolution."