We build all of the examples on the jqxTabs’s Getting Started, and they all seem to be running just fine. Did you include the files needed to build your code in the JS Editor? If you haven’t the easiest way of doing that is just go to the file button in the top left and select open. After that just select JQWidgets Templates, it has most of the core files needed to run your code.
Hope this helps.
You should go to project then libraries, then go to the Add button(the plus icon) and add these: https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.min.js https://www.jqwidgets.com/public/jqwidgets/styles/jqx.base.css https://www.jqwidgets.com/public/jqwidgets/jqx-all.js