The error "QR is out of date" means that you are trying to use an expired code. Please call up the QR code scanner and scan it again.
When creating an account, you specified an invalid username/password or there is no access to the domain (if you have a domain account). Go to the account and edit the data.
The computer you are trying to unlock has no connection to the server. Just wait and try again.
The phone has no connection to the server. Just wait and try again. OR The phone is not connected to the Internet. Check and connect.
The computer is already unlocked.