You can try below steps also. It might not be a JRE issue as it is not working with HTML5 plugin also. [URL] [URL]  [URL] 
We're having an issue with connecting to the virtual console for our PowerEdge hosts. When launching the virtual console I get the following message:"The viewer has terminated.Reason: The network connection has been dropped." I'm running:Java version jre1.8.0_261BIOS: 2.11.0Firmware: 2.70.70.70 Trying to connect with the latest version of Chrome, Firefox and Edge has the same result. Anyone have any suggestions? I've tried modifying the java.security file but nothing I've tried works. Our server is out of warranty so there's no support there. Any other information that can be helpful here to provide please let me know.
IDRAC 8 Virtual Console Fail To Connect