This error is caused by attempting to perform a STCMD operation using an encrypted password file, without passing the username in the connection string.
stcmd co -x -epwdfile "C:\epwdfile" -is -o -p "@server:49201/StarDraw/StarDraw"
As the username is missing, STCMD cannot connect. The command above should be edited to include the username as follows:
stcmd co -x -epwdfile "C:\epwdfile" -is -o -p "user@server:49201/StarDraw/StarDraw"
The username specified should be the username for which the ewpdfile password was stored.