1. First, check to ensure you have installed Adobe Flash or not. You may need to install Firefox instead of using Chrome. After the installation of these two, you can see the mobile version of YouTube site works fine with Firefoxbeta.
2. Try to clear cache or any data of YouTube app in the settings, then soft reset Nexus 7.
3. If these two options does not work, you will need the help from other apps:
- First, tap on the Home key to return to your Nexus 7’s Home screen.
- Launch Google Play Store app.
- Next, search and install Titanium Backup from Google Play Store on your Nexus 7 tablet.
- Launch the app.
- Press the Backup/Restore tab at the top of the screen.
- Then find and select the YouTube app.
- Finally, hit the Wipe data key.