If the batch file runs fine when run manually under a logged-in user, test the scheduled task by seeing if turning the option to only run when the associated user is logged in on changes anything. Log in as that user and force it to start, see what happens.

Mapped drive references may not work without a logged in user, so if you find that the scheduled task launches with that option changed you have two choices:
- try and purge all mapped drive references from any part of the system that will be in use during FX retrievals, replacing them with UNC references
- keep the user logged in to run the task