Hi Gunjan,

The very first common complaint with YouTube videos is the screen turning black during the loading process. The page loads but the video does not stream. I think you are also facing this issue.

You can follow the below methods in order to resolve this issue and continue watching YouTube videos online in your browser:

Method 1. Uninstall and Reinstall Adobe Flash Player 

This may fix the flash video issue and it may not, but it’s worth a shot. Start by jumping to the official Adobe website and downloading the Flash Player uninstaller for OS X. Launch the uninstaller and simply uninstall Flash Player from your Mac and restart the computer.

Once your computer boots back up and you’re signed in, proceed to Adobe.com to download the latest version of Flash Player.
Reinstall and check to see if YouTube videos are working.

Method 2. Try to disable Flash hardware acceleration

While on the screen of the blank YouTube video that is not working correctly, right-click the area where the video would normally show up to bring up the Flash Player context menu.
Select the Settings option from the menu. Unselect the option Enable hardware acceleration and click the Close button.
Close out of the browser completely, relaunch and test YouTube videos.

Method 3: Delete cookies from your browser

All cookies should be deleted from YouTube cookies. You can remove first-party and third-party cookie information and data from your devices.

1. On your computer, open Google Chrome.
2. In the top right, click the Menu .
3. Click Settings Show advanced settings.
4. In the "Privacy" section, click Content settings.
5. Under "Cookies," click All cookies and site data.
   • To delete all cookies, click Remove all.
   • To delete a specific cookie, hover over a site, then click the that appears to the right.

I hope this should work for you.

Regards,
Lokesh