vpk modding isn't working, does anyone know a solution?

I've been trying to use vpk modding to change the l-star's crosshair, but every time I try to run the game while I use the files that have the crosshair altered, I get the following text when I boot my game

"engine error can't find background image materials/console/product_1_widescreen.vtf"

I'm a bit confused since I've never altered anything else, does anyone know what may be causing this? I'm playing the vanilla servers using EA and not Origin, if that makes a difference