The SSL certificate has been successfully provisioned using SSLStore Certificate Plug-in. When downloading it from control panel Parallels Business Automation> Services> Certificates> select your certificate > Download Certificate, only
CACertificate-1 gets downloaded.
The issue is reported as bug with id #PBA-58057 ("A wrong SSL certificate is downloaded for the SSLStore Certificate Plug-in")
The bug is fixed in PBA 5.5.7, please update to that or later version. In the earlier versions it is possible to get ServerCertificate by downloading the whole chain ("Download Certificate Chain").