RHEL5 Registration Problem

Hi ,

I have a problem with RHEL 5 registration on idm .
Outputs are like this:

ipa-client-install --domain=example.com.tr --realm=EXAMPLE.COM.TR --server=unixidm.example.com.tr --hostname=$(hostname).example.com.tr --no-ntp --mkhomedir --principal bind
.
.
root : ERROR Cannot obtain CA certificate
'ldap://unixidm.example.com.tr' doesn't have a certificate.
Installation failed. Rolling back changes.

And then ı would try like this :

ipa-client-install --domain=example.com.tr --realm=EXAMPLE.COM.TR --server=unixidm.example.com.tr --hostname=$(hostname).example.com.tr --no-ntp --mkhomedir --principal bind --ca-cert-file=/etc/ipa/ca.crt
.
.
Joining realm failed: HTTP response code is 403, not 200
Installation failed. Rolling back changes.

only redhat 5 mistaken ,other versions (rhel6 , rhel7) haven't got this problem. Anybody help please..

Thank you.