yeah, i've noticed the game doesn't properly copy over some of the required files. skyboxes are another one. i'll put a mirror download link in the description

the workaround for this issue is to copy the wad files from "steamapps\workshop\content\3416640\3554881574" and paste them into "steamapps\common\Cross Product\zamnhlmp"

some maps crash the game because the game can't load .wad files from workshop items