PFClean makes extensive use of GPU acceleration and as such it needs access to the graphics card. This can lead to some issues.
On Linux, X11 must be running and the X server accessible. Typically this means a user must be logged in with the desktop showing and
xhost +local: executed so that the batch job, potentially running as a different user to that which is logged in, can access the graphics card.
On Windows, a user must be logged with the desktop showing.