Custom Workspace and Workspace Sidebar not visible in UI on Production

Actual Behavior

Workspaces can be opened directly using their routes but do not appear in the Desk workspace/module navigation.

Expected Behavior

The custom workspaces should appear in the workspace/module navigation like standard ERPNext workspaces.

Has anyone seen this on v16 or Frappe Cloud? Is there any additional configuration required for custom Module Def / Workspace combinations to appear in the Desk UI?

Thanks.