Why Can I Not Play Media Files From A Mac Formatted External Hard Drive On My Hdtv

I formatted it for Mac OS extended, so I could obviously store files from my Mac. Although when I connect my hard drive to my HDTV it would not play or even recognize files on it.

I used to do that with my PC and other hard drive all the time - and it used to play media of all kind of formats. Is it because it was reformatted for Mac or what?

Thanks for answers