Answered: "Not authenticated to the server." - error on executing SFTP putfile command C#

Please make sure you call both the Connect and Login methods before calling PutFile/GetFile, and that the Login method actually succeeds. If you don't find any problem, create a communication log using Sftp object's LogWriter property and either post it here or mail it to support@rebex.net. Based on the log, we should be able to tell what is going on.