Hello, Reinstall the extension after an older version is uninstalled:

http://download.sf-helper.com/mozilla/helper_last.html

Ок.

По присланной информации у Вас не установлен или выключен помощник.

Переустановите расширение прежде удалив предыдущее если помощник у Вас установлен.

http://download.sf-helper.com/mozilla/helper_last.html

https://en.wikipedia.org/wiki/Proxy_server

In order for us to help you, kindly answer all our questions.

Hello, we’d like to help you, but we will need some info about your browser and the installed extension first.
Please, go here http://en.savefrom.net/user.php?info=1,
copy the details that you see and send them back to us.
Please also send us some video links that you can’t download.

Do you download via the extension SaveFrom.net Helper or the website SaveFrom.net?
Thank you for contacting Savefrom.Net support !

Can you watch youtube videos in the browser before you are trying to download it?

Do you use any proxy?

Send us screenshots of how you download videos.

You can describe your problem in more detail?

Can you watch youtube videos in the browser before you are trying to download it?

What’s your country? Do you use any proxy?

Send us screenshots of how you download videos.

Clean the cache and cookies in your browser.

Most likely, you have a "network break", use the program Download Master.

We have nothing to do with blocking the Youtube site.

Hello, in order to download, the video should be available for viewing on the Youtube website.