Hello, after showing the playback, click on the video with the right button and save as.

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, unfortunately we can not influence this, downloading is done directly from Youtube.
It is the site Youtube gives with this name.

Hello, the video on the link is not available, we can not verify it.

Hello, in order to download MP3 from Youtube you need to install our program Ummy Video Downloader,
Also with the help of it you can download videos in high quality with sound: https://videodownloader.ummy.net

Hello, please give us more details.

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

We do not quite understand you, if you have a problem, kindly describe it in more detail.

Hello, in order to download MP3 from Youtube you need to install our program Ummy Video Downloader,
Also with the help of it you can download videos in high quality with sound: https://videodownloader.ummy.net

The program is downloading this video

The question mark on the green arrow is an instruction on how to use the extension,

By clicking on the green arrow you can read it or close it.

We can not understand in what there can be an error.

We can advise you to do a full cleaning of the browser, but it's up to you.

https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings