Unable to play videos on KDE web page

This is puzzling me. I have codecs installed via opi codecs and I can watch anything I want with firefox (including netflix, TV media centers)…
…except the Plasma 5.25 demo videos at

Whenever I click on a video, the controls show me that the video got started (by displaying the pause button), but that’s all.

If I inspect the videos, I can see two different versions behind:

If I copy these URLs and paste them into a new tab, the videos play without any issues.

Is there anything else I need to do to play these videos?

Same here, FF102.0.1 - Leap 15.3.
Seems to be a cookie issue. Try allowing cookies for the session in page info “ctrl+i”. Worked for me. Blocking them and reloading with ctrl+F5 reproduces the issue.

That happens here, too. But they play in konqueror.