When I activate Smush pro or Smush I immediately get a 500

When I activate Smush pro or Smush I immediately get a 500 error on my site:
500 - Internal server error.
There is a problem with the resource you are looking for, and it cannot be displayed.

The site is hosted on Amazon with a windows server. Is that not compatible with Smush? Or is there anything that I can do to resolve this.