UPDATE: STILL WON'T WORK TO COMBINE ANY AUDIO/VIDEO FORMATS! TOTAL PIECE OF CRAP!
I FINALLY GOT IT TO INSTALL PROPERLY & CONFIG IOT PROPERLY, & IT WON'T COMBINE THE SEP AUDIO & VIDEO, IT DL'S THEM SEPARATELY, & WON'T COMBINE, DURING, OR AFTER DL. & WHEN I TRY & COMBINE THEM IN THIS ADDON AFTERWARDS, I GET AN ERROR MSG WHEN I ADD THE AUDIO FILE! I RE-DL'D THE DAMN VIDEO FROM YT A 1/2 DOZEN TIMES SINCE YESTERDAY, SAME DAMN THING!
WHAT GOOD IS A LIVE CONCERT VIDEO W/OUT SOUND? SERIOUSLY? IF THE DAMN VIDEO HAD THE OPTION OF BOTH AUDIO & VIDEO IN ONE FILE (WHAT A NOVEL IDEA!), THEN THIS WOULDN'T BE AN ISSUE! BUT, THE ONLY COPY OF IT WHICH DID IS ONLY 360 RES! TOTAL CRAP! BUT 720+, THE AUDIO & VIDEO ARE SEP DL'S! IF THIS ADDON ACTUALLY WORKED, LIKE IT CLAIMS IT DOES, THIS WOULDN'T EVEN BE AN ISSUE!

Everytime I try & DL a video w/this addon in FF V. 57, I get the following msg.:
"Welcome to Media Converter
In order to use this conversion tool follow:

Download this minimal native client
Unzip the downloaded package
Install the native client:

↝ Right click on Install.bash and select "Run as administrator"
Click here to check the native integration"

I do these things, & the addon STILL gives the same msg. Over & over again! & when I 'Click here to check the native integration', literally NOTHING happens! This used to work flawlessly in older browser versions, but sadly no longer does in the latest version! Fix this already would you guys?