If you're having trouble using your PIN to sign into Windows 10, log in with your password and reset your PIN. Follow these steps:
On your lock screen, under the PIN entry box, select Sign-in options and sign in with your password.
Select Start > Settings > Accounts > Sign-in options, and select I forgot my PIN.
Follow the steps and create a new PIN.
Note: If you've just updated your computer to Windows 10, verify your network connectivity by opening Settings > Network and Internet. After connecting, try signing in with your PIN again.