Well, seems Java’s runtime environment has gotten more strict as new versions of it came out. When you load an applet and you get this message
java.lang.SecurityException: Your security settings have blocked an application from running with an insecure or expired jre.
There is only one solution as a user to make the applet run. You will have to lower the security settings in your Java settings.
Go to Control Panel then open Java icon. Go to security tab and set the security setting to medium. That should run the applet.
Just be sure you trust the publisher or else your PC will be at risk. This is the only solution possible since the other way is to wait for the publisher of the applet to repackage the jar file with manifest attributes that will enable the latest Java runtime environment to run the applet.