[ovirt-users] ovirt 4.0 after set the host into maintenance and then "Enroll Certificates" but the install failed

hello everyone, my ovirt-engine and host certification is expired, is it any method no need to shutdown all the vm can enroll/update the certificate between engine and the host??? i am using the ovirt 4.0 i tried to set the host into maintenance and then "Enroll Certificates" from the UI but the engine also show install failed thank you