The page specific CSS on sc_cat_item does not work when the page sc_cat_item is accessed via csp and csm portals.
Release or Environment
This is caused by the OOB page route map on CSP/CSM portal and sc_cat_item page. This page route loads csm_sc_cat_item page when sc_cat_item page is accessed via the CSP/CSM portal.
Add the Page Specific CSS to the csm_sc_cat_item page instead of sc_cat_item to have the CSS in-effect on the CSP/CSM portals.