Resources / Users are not visible in Home -> Resources list page / portlet. This page does not show any records. When the srm_resources table is queried, all the records that are supposed to be shown in the page are returned.
Home -> Resources page runs a Select statement in the backend that joins srm_resources table with the prj_resources table, amongst others. There were no records present in prj_resources due to an incorrect refresh of the DB schema from Production.
Perform a fresh refresh of the non-production environment's DB.