Looks like you're using adTempus 3.x. This doesn't appear to be documented anywhere but the user account that the job is running under has to have permission to log in to the remote adTempus instance and to execute the target job. So you will need to edit the security settings on the remote adTempus instance and grant login permission to the user, and then grant the user Execute permission on the necessary jobs.

Beginning in version 4.0 this is handled differently, through Linked Server settings, and permissions are checked against the user who is creating/editing the job, rather than against the account the job runs under.