Hi

I downloaded the 30 day trial version of lync (for professionals and small businesses) from office 365 and installed on Win8. However, I cannot sign in after installation, even using my administrator account. I created my own domain on the standard extension (.onmicrosoft.com).

The error reads: "Cannot sign in to lync. There was a problem verifying the certificate from the server." 

Thanks in advance for the help.  

Hello Water,

The Error is occurs when the certificate get expired, Follow these steps to Renew the Certificate:

Error : "There was a problem acquiring a personal certificate required to sign in. If the problem continues, please contact your support team."

Cause : If the user’s root certificate is corrupted or it get expired

Resolution : Renew the certificate in Windows Certificate Manager, To do this follow these steps:

1. Click on Start >> Run >> Type certmgr.msc >> Click Ok
2. Expand Personal >> and then Expand Certificates

3. Look for the certificate check whether it is not expired

4. If the Certificate is expired right click on it select All Tasks >> and then click Renew certificate with New key. Follow the Screen Instructions to Renew the certificate.

5. Try to sign in to the Lync online, If you cannot sign in delete the Certificate. Then try to sign in to Lync Online again to download a new certificate.

Hope this Helps!

Kind Regards,

Surya Begum.