The following message can occur during a LockDown Browser integration test if you have invalid or incomplete SSL certificates:

"Your SSL certificates are not valid. Self-signed certificates are not supported by Respondus LockDown Browser. If your certificate is not self-signed, please make sure it has not expired and that all intermediate certificates are also installed in your server. You can use this Certificate Checker Tool to verify your certificates."
 
Respondus servers will try to connect to the LMS specified in your Respondus profile. If the SSL certificates installed on the LMS server don’t match the domain, then the SSL error will occur. 

In general, it's necessary to ensure that the SSL certificates installed in your LMS server are the correct ones for your domain. You also need to make sure all the required certificates are installed. Most setups require at least two certificates: one specific to the domain and one intermediate certificate.

This particular SSL error will happen if you only install the domain specific certificate but not the intermediate one. It can also occur if you install the wrong certificate(s).