Replace
var kbPortal = new KBPortalService();
with
var kbPortal = new sn_km_portal.KBPortalService();
I believe you cloned Knowledge Article Content widget in scope sn_km_portal to Demo Knowledge Article Content n global scope. Script Include KBPortalService is in sn_km_portal. The cloned global widget has to prefix the scope name to initialize the script include.
Regards,
Rajesh
var kbPortal = new KBPortalService();
with
var kbPortal = new sn_km_portal.KBPortalService();
after that clone the script include kbPortal Service with the same name and apply it to all scopes and disable OOB script include and work with this cloned one script include