CASES:
1).Some time it happens due to Java ssl certificate check , did you added the Appliance IPMI ip to Java's Security "Expection site List" ?.
Please verify once by going to Control Panel --> Java --> Security settings and add the https://yourapplianceip.
if you are already added means please ignore.
2).And we are sure you need add the Appliance IP to Internet Explorer Security --> Trusted sites and make a custom configure for Trusted sites enable all the settings expect the " Use Pop-UP Blocker".
3). Antivirus or Windows Group policy might blocking the java jar files to execute.