Via Google –

“Certain older YouTube apps will no longer be supported after April 2015

Devices affected: Select devices manufactured in 2012 and earlier, including Sony TVs & Blu-ray Discs, Panasonic TVs & Blu-ray Discs, older iOS devices, and devices running older versions of Google TV.

As we upgrade the YouTube Data API to bring more features, we’ll begin shutting down the old version on April 20, 2015. This will result in the current YouTube app not working on certain device models from 2012 and older.

We will continue to focus our efforts on improving our official YouTube app for TV which is available on most 2013 and newer Smart TVs and Blu-ray players, game consoles and streaming devices”

How can I continue using YouTube?

– iPhone, iPod Touch, or iPad – If your device supports iOS 7 or above, you can download the YouTube app from the App Store. If not, visit m.youtube.com in your mobile browser to access YouTube.

– Apple TV – If you’re using Apple TV 3rd generation, you can get the latest version of the YouTube app by updating your software:

Select Settings > General > Update Software
If there is an upgrade available, click Download and Install
If you’re using Apple TV 2nd generation or older, unfortunately there’s no current way to watch YouTube on these devices

Source – https://support.google.com/youtube/answer/6098135?p=yt_devicesupport&hl=en&rd=1