Vitaly,
It seems that the certificate on your test server is no longer valid. Either, it's expired or it's changed and hence, the machine where you launch the test from is not updated with the new certificate.
It’s possible that your server uses self-signed SSL certificate that is not added to your default truststore. You can use Set_Ssl_Settings command to replace default truststore with a custom one within test case execution. Please, contact your administrator to provide you with a keystore and truststore files.
Regards,
Subject7 Team