Are you still having the problem?
I searched a little bit online and i got this. You may try...
* Browser
1. Open Google Chrome on your computer.
2. In Google Chrome window, on the right-hand side, click on ‘three-dot‘ and then click on the “Settings“.
3. Now, scroll down through the Chrome settings and then click on “Advanced“.
4. Under System, toggle “Use hardware acceleration when available” to “Off“.
5. Click on “Relaunch” to restart your browser.
Once the browser is restarted, try to play the YouTube video again.
* YouTube app
1. Restart the YouTube app.
2. Restart your device.
3. Turn off and on your mobile data connection.
4. Clear the YouTube app's cache.
5. Uninstall and reinstall the YouTube app.
6. Update to the newest available version of the YouTube app.
7. Update to the newest available version of Android.