Why won't video play on some websites?

My understanding is that over time, updates to FF, Chrome or Safari modify settings somewhere, or other updates to your Mac do so, and you're likely to have a conflict. Getting back to the original settings and then slowly adding the changes back may isolate what is causing it. Extensions and add-ons to browsers are prime suspects.

In the meantime, what I do is have my iPhone to hand when looking at websites that won't display video. I use the iPhone to look up the same site and run the video. It's annoying, but works. IOS is simple but very robust.

Hebairt

I solved this problem by removing AdBlock Plus and Ghostery, which are extensions I use on both Safari and Firefox. I think the Telegraph running ads before some of their video clips may have triggered something in AdBlock Plus that prevented the ads running. You might also try right-clicking on the video itself (or rather, the blank screen) and if you see an option to load the video in the Dashboard, try that and play around with it. Good luck, and thanks again to Linc.

Just to add that you should remove Adblock and instead look for a similar thing called Simple Adblock. It removes the ads that run before Telegraph video but lets the video run. However, Ghostery definitely stops the videos opening, to fix it you need to edit blocking options for Ghostery to allow all trackers on Telegraph's website. WHen you see how many there are, you may decide to do without the video...