JMX Configuration Generator admin page fails

When I click on 'NEXT' button on JMX Configuration Generator page, the UI reports an error in a separate box. This error is not reported in the logs. This is the same with the opennms-jmx-config-generator.noarch 0:16.0.0-1 rpm installed or not.

The full error is not visible on the page so only part of it was copied below;

rg.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:255) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:154) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116) at org.eclipse.jetty.server.Server.handle(Server.java:364) at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489) at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:953) at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:1014) at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:861) at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:240) at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82) at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628) at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608) at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543) at java.lang.Thread.run(Thread.java:745)