Solution : https://service.sap.com/sap/support/notes/1066190 (SAP Service marketplace login required)
Key words : 
configuration > workflow > stage >stage configuration > additional configuration > approver stage, prerequisites stage definition, access enforcer request approval, compliant user provisioning, request level solution, reject button greyed, approve/reject request, approve button greyed, approver stages, access enforcer
Related Notes : 
       
| 1483367 | Restricting GRC CUP permissions to Display only mode | 
| 1228996 | Manager Details Not Shown. |