If you are getting this error “Error: 3 (unknown authentication error 3)” when you attempt to obtain tokens using OpenAFS for Windows, you forgot to install Kerberos for Windows, KfW is not configured correctly for your realm, or you do not currently have a Kerberos TGT for some other reason. The error is returned because the AFS client cannot obtain tokens if you do not already possess a Kerberos TGT.