Verify that the new certificate appears and marked with a small blue point with a white plus sign in it. Now, in the Keychain Access application, navigate to System under Key chains and select Certificates under Category on the left pane. the Lync Configuration Information option on the Lync client actually provides a lot of useful information about how the client connects to the server and can help identifying issues.You will be asked to insert your password again, insert it and click “Update Settings”.Then click “Always Trust” on the popup window. Expand Trust by clicking the small arrow next to it and verify Always Trust is marked.The Keychain Access Insert your password and click “Modify Keychain”. You will be asked to put in your password to approve the Keychain modification,.The following message will popup, change the Keychain to “System” and click ‘Add’. Locate the certificate file (.CER) you have received from your system administrator and double click it.Open the Keychain Access application, you can find it in the Launchpad or find it with Spotlight.The following guide was written by a colleague of mine, Lior Gilboa and it explain how to install a root CA certificate on a MAC client: Those root CA certificates are required in order to sign-in into Lync rather it’s on the internal or external network. Recently we got some support request tickets regarding MAC clients which weren’t able to sign-in into Lync because they were missing the necessary root CA certificates.
