the code capture feature (and the red button) is hidden by default. In order for it to appear, you have to navigate to Developer Center > Code Capture, and enable code capture through the toggle. The setting will be persisted across sessions, so you won't have to enable it every time.
I installed the HTML5 fling in order to use code capture. The HTML client works - I am able to log in, and see the UI, but the code capture red button is missing.
I installed the fling from h5ngcVA-188.8.131.52-13172979_OVF10.ova with VCSA 6.5 build 4944578
Is there anything I have missed in the installation steps, or something else is wrong?