Developers of Youtube have done you can not install the Youtube application on the old version of Android (for example, Android 4.0).
You need to remove the official Youtube application and install another program.
It's called OGYouTube. For Android 4.0, OGYouTube version 10-45-53 is suitable.
Download OGYouTube from site Uptodown, from here -
First you should enter this site, next scroll down the page, then to choose the version of OGYouTube 10-45-53 (for Android 4).