Channel 4 won't play why?

As there are more than a few around, which Channel 4 are you referring to here?

What happens when you try? Any error messages or diagnostics shown?

Please download and run and post the hardware and software configuration output of EtreCheck here, and then after opening a reply here, and then pressing the(highlighted) button to create a text input box here in the forum that's big enough for the report, then paste the configuration report int the text input box:

I read about mixed troubles on a UK site I visit, but it seems up or OK here...

https://downtoday.co.uk/channel-4-on-demand/

Maybe it's an Internet or ISP problem?

Seems OK here, at least this far...

https://www.channel4.com

My channel 4 works great.

hey... that's not your channel 4, that's my channel 4! :P

OK, I'll take this channel 4.

I hope the original poster gets the point. He needs to be more specific when posting about an issue.