Parallelpiped Source not generating particles?

Hello everyone,

I’m running the following macro GPS file off of example B1:
(whole macro not included for brevity)
/gps/particle gamma
/gps/pos/type Surface
/gps/pos/shape Para
/gps/pos/centre 0 0 0
/gps/pos/halfx 90 cm
/gps/pos/halfy 44 cm
/gps/pos/halfz 44 cm
/gps/pos/paralp 90 deg
/gps/pos/parthe 90 deg
/gps/pos/parphi 90 deg
/gps/ang/type/ cos

What I’m more or less trying to create is a uniform fluence across a rectangular prism (with my scoring volume on the inside). I have a user defined energy histogram that Im using. However, when I run any number of particles, for some reason it doesn’t seem to generating. Whenever I use any other particle type, it works perfectly fine and when I visualize it, it looks more or les show I think they would look.

Any suggestions is much appreciated!!

U can follow the GPS examples on the website: