Export SWF issue

(Using Harmony 21)

I have all of my Export and Write node settings set by default, but when I try to export in .swf - it says that export was successful, but the generated SWF’s size is 1 Kb and the result is empty.

Also, when I preview the output (Test SWF Movie) it says that it was successfully rendered, but when I press “Ok”, this pops up and the render doesn’t show up:

What does this mean? How can I fix it?
Is this feature still supported?