Solution for can not find "Manage Private Key" option in service security certificate !
When you right click on the security certificate in MMC you might not be able to see "Manage Private Key" option.
The restoring of private key is the solution of this situation.
Copy the thumbprint of security certificate and run the command prompt as a administrator and use the following command to restore private key.
certutil -repairstore my "thumbprint of security certificate"
This is the example :-
certutil -repairstore my "5e 50 3b 23 dc 26 c3 aa 90 b2 d0 96 10 df 8b 7e 28 54 80 20"