Hi @SalvoAbbru
You could try to add the certificate to the Java Truststore with the keytool (https://docs.oracle.com/javase/6/docs/technotes/tools/solaris/keytool.html)
Maybe the KNIME.log will provide a little more info about the problem. You can find it in at “View”->“Open KNIME log”. You can send it to me via private message so I can have a look into it too.
Best regards Mareike