Update the extension.

Hello, send a link to the video for testing.
For the better understanding it'll be great to see a screenshot with the error. 

Hello, in order to download 1080p with sound from Youtube you need to install our program Ummy Video Downloader,
download video with sound through the site or an extension there is no technical capability: http://videodownloader.ummy.net

Hello, send a link to the video for testing.

Hello, please, send us more details regarding the problem.

Hello, thank you for contacting support in Savefrom.Net
This bug is known to us, we will try to fix in the nearby future.

Hello, Could you please send a few links you can't download. We will check it out.

Do you download via the extension SaveFrom.net Helper or the website SaveFrom.net?

For the better understanding it'll be great to see a screenshot with the error. 

Hello, thank you for contacting support in Savefrom.Net
This bug is known to us, we will try to fix in the nearby future.

Hello, please give us more details.

Hello, please, send us more details regarding the problem.