I don't remember exactly what I did with that project years ago.

But I am sure that no need to install anything extra on AS400.

If you directly run SQLCMD from Windows...

Here is my example:

RUNRMTCMD CMD('sqlcmd.exe -S "MY-SQL-SERVER" -Q "execute msd

b.dbo.sp_start_job @job_name = ''TestOnly'' "

...

In fact, you can try to directly run the command on the server (your RUNRMTCMD destination) to see if it starts the SQL job.

You can add >> c:\temp.txt to redirect the command output to check if the job started successfully.

Also make sure the user is a member of SQLAgent*Role in msdb.