Hi Jan,
Have tried an ubuntu image on AWS following all the instructions as per your link and I still get exactly the same error! I have tried running and express app which calls an oracle db to return json data and this works perfectly. Are there any other prerequisites that are required for the JSreport install ? FYI my test client machine is a windows box running chrome browser which is hosted on premise. I can install JSreport on windows locally and it works fine. We have an AWS security policy to allow port 5488 from our client machine to the JSreport server. The URL we are using in browser is http://awsipaddress:5488 which brings up the studio fine.