The category.php file was looking for the groupsaccess.php file in the wrong place. it was looking in:
include_once(XOOPS_ROOT_PATH."/include/groupaccess.php");
but the file is in:
include_once(XOOPS_ROOT_PATH."/modules/wfsnippets/include/groupaccess.php");
thanks for the pointer Herko,
abdala