Alguém teve e conseguiu resolver essa mensagem no teste da conexão do PDI com o SQL Server:
The driver could not establish a secure connection to SQL Server by using Secure Sockets Layer (SSL) encryption. Error: "sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target". ClientConnectionId:a182ec26-fe43-44a4-82a9-807463a9060a