[Windows Central Question]

I had youtube app on my window 7.8 phone but suddenly it started not to open the videos. When I click on the videos and a warning comes up saying we cant play this file on your phone.

[SBoelitz]

Is this on all videos on youtube I know that people who upload videos to youtube can disable the ability for it to played on a mobile. I cant remember if WP 7.8 has this feature or not but in the IE settings can you change the mode from mobile version to desktop version under website preference?

[zdravez]

I noticed the same behavior on my dell venue pro.

[dKp1977]

Try to open YouTube in your browser and play the files from there. This should work. Google recently changed the API for YouTube, which rendered all the YouTube apps useless. Developers quickly updated their apps to make use of that new API so that videos could be played again.
Since Windows Phone 7.8 is dead so to say, I think developers of YouTube apps for this particular OS iteration don't care updating their apps anymore, which is why your app can't play the videos.