communicator cannot connect to the server because the required security is not in place (Solved)

OCS client is  not able to expand users in any of the AD group lists . It is showing error as below

“Communicator cannot connect to the server because the required security is not in place”

Solution:

The issue was with the certificate which is not providing a secure channel between the user computer and the server

I tries the below links from the user system and found it was showing a certificate error

https://ocspool.yourdomain.com/abs/int/files/Sample_Company_Phone_Number_Normalization_Rules.txt
https://ocspool.yourdomain.com/conf/ext/Tshoot.html

Note: where ocspool.yourdomain.com is the FQDN of the OCS pool

Then I installed the certificate from the IE itself and the issue resolved