Thread:Extension talk:ChapTimeline/ChapTimeline doesn't display anything

I installed Semantic MediaWiki and ChapTimeline today, but couldn't get the latter to work. My #ask query works okay, i.e. it displays data nicely as long as the "format" parameter is not "chap-timeline". If it is, the generated HTML is

but nothing is displayed there.

I also installed the InteractiveTimeline extension which works flawlessly.

Thanks for consideration!