There is an error in the in the server password or a template setting.
Here is the documentation. Pretty straight forward
Login to the Server was not possible during Scan to Server file transfer.
Initial Action
Refer to BSD 16.1.
Power OFF/ON
Procedure
Set the login name and password in the destination server.
Set the attributes of the Job Template file correctly.
From a client PC, set the same account as the above as a resource using CW.