Tubepress Video Popups are Blank

How do I fix blank video popups on this site? http://anetteprehn.com/blog (Click the right column videos)

What I tried so far:
I re-installed TubePress 3.1.5. I also temporarily disabled all plugins except TubePress, didn’t help.

Other Information:
When I test TubePress on my localhost server, the video popups work.
I’m using the TubePress widget.

Thank you for your time,
Bryce

https://wordpress.org/plugins/tubepress/