Simply put it's not working and hasn't been since YouTube went full on nuclear to break this and other downloaders. We're shit out of luck when it comes to downloadng YouTube videos until someone comes up with one that works and is unbreakable - or this developer fixes this downloader. We can only hope and wait...
When there are more 1-star reviews than 5-star reviews there's your sign it's not worth installing...

Doesn't work.
Junk

Not working

it isn't working for me

does absolutely nothing - 100% CR@P

there’s no MP3 download available

НЕ РАБОТАЕТ!

Автор ПИДАР!!!

not working

Doesn't work.

Doesn't work

Doesn't work.