Slideshow plugin (by Stephan Boonstra) not loading custom css

I’m having problems getting the custom css to load using the slideshow plugin. The CSS in the correct style sheet and I have the slideshow using the correct stylesheet. However, when I go to view the page source the custom css isn’t applied at all.

I am using the same plugin on other sites and the same custom css and I have not had this problem before. Any thoughts? Thank you!