At this moment, WP ERP does not have any option that will enable WP ERP to work smoothly with LDAP and all of your users are on LDAP. For those reasons, the system unable to detect employee until they signed in.
Please make sure that you have created the leave policy because without this, leave request feature will not going to appear.
You can check leave management, configuration from here: https://wperp.com/docs/hr/leave-management/
After doing all this if you still face the same inconvenience then I recommend you to create a support ticket from here: https://wperp.com/contact/. The WP ERP’s specialized team will help you there with the best way possible solution.