If you try to connect lync from internal network (nondomain computer), you will see error: “There was a problem verifying the certificate from the server. ”

if your domain computers work well and you have this problem only for nondomain computer then it occurs, because certificate which is issued for lync front end
server is not trust for non domain computer.
to ensure
export lync front end certificate from lync server (Certificates(Local Computer)\Personal\Certificates) without private key



copy this certificate to nondomain computer and open it. you’ll see

to solve this problem you must import your root chain in nondomain computer. in my case i’ll export root chain from domain computer

and import it in nondomain computer (From mmc in computer certificate store )

after it open certificate which you export from lync front end server again.

it means that certificate for lync front end is trusted certificate for your computer, restart your computer and try to log in lync from internal network. There is no certifcate error :) .

P.S for domain computers this root chain automatically is installed from domain.