Schannel: Certificate received from the remote server was issued by an untrusted certificate authority

Solution 1:

You probably receive this error because a program (SQL Server in your case?) is trying to access a remote resource over an SSL connection but, the SSL certificate used by this remote resource is not trusted by your server.

To find which remote resource your server is trying to access, in Event Viewer, open the Details tab of the event (use the Friendly View). Here the EventData contains the SSL certificate received.

To understand the EventData, scroll down until you see the section In Bytes. Here on the right the Event Viewer decodes the data in text and you should be able to see among all these weird characters a URL, a userPrincipalName, or something like that.

Note: in my case (test lab), my server was trying to access something on my domain controller. Adding the certificate of my DC to the trusted root store solved the problem.

Solution 2:

I just saw on Microsoft's site that this is a known issue all the way back to Windows 7. It must still be an issue since the article was just updated a few days ago. Their answer is to turn off Schannel logging and that "this will be fixed in a future release."