I had the same problem with jbpm-5.2.0.final. I installed using "ant install.demo" and started eclipse etc using "ant start.demo". It turned out that only the first Human Task View and Process Instances view can connect. Which means if you have those views opened in multiple perspectives like Debug and jBPM, then make sure only use them in Debug perspective. The Eclipse installed by jbpm installer opens jBPM perspective by default and it's tempting to try it out there and then it won't connect in debug perspective until restart Eclipse.