The maya_app_dir is the set of directories that Maya creates (usually under your home directory) that contains all the prefs/scripts/ etc directories the first time the Maya GUI is launched.
You'll need to create this directory structure for the user who is running the job by logging into the worker as the user attempting to run the job and starting maya.
I would check and see how your other workers are setup. Are they running in proxy mode? If so, someone probably logged in once as the proxy user and started maya once.
If they run in user mode, are all the users' home directories mounted from the network?
