I have been several day to getting AD over SSL (LDAPS) I followed exactly this guide. I have Active Directory Certifica Service installed (stand alone Root CA), I can request cert, install certs.

but whenever I want to test the connection using LDP.exe

I got this famous error

ld = ldap_sslinit("localhost", 636, 1);
Error 0 = ldap_set_option(hLdap, LDAP_OPT_PROTOCOL_VERSION, 3);
Error 81 = ldap_connect(hLdap, NULL);
Server error: <empty>
Error <0x51>: Fail to connect to localhost.

I have been searching, I know there are many thing can cause of this error, I tried most thing I can then I decided to post it here. I tried to look if any error in system log, but nothing :/ (but I could be wwrong)

can anyone tell me what else to look?

UPDATE: I restarted AD service following error showed in event viewer:

LDAP over Secure Sockets Layer (SSL) will be unavailable at this time because the server was unable to obtain a certificate. 

Additional Data 
Error value:
8009030e No credentials are available in the security package