1-Please check whether you have been logged in with same Hr which is mapped during separation manager mapping.
2-Please check if employee Date of Leaving is over in that case also employee will not Reflect in Hr revoke Screen.
3- If the employee status is changed to HOLD , Resigned then the employee will not be visible in revoke screen.
These are 3 checks that need to be done if the employee is not visible in the revoke screen