UPDATE! Now it still has errors everytime I try & merge audio/video, & when it succeeds, the file is only 22 seconds long! WTF is the point in THAT?! SMDH! Fix this shit already, please, would you?

It won't combine both the video & audio for vids DL'd via YT, & I have the latest FFMpeg installed too! & it is all config'd properly but yet will NOT combine both when DL'ing, & when I try & combine them afterwards in Media Muxer & Converter, it gives an error msg everytime I try & add the audio file to the video combiner. This addon USED to work just fine, flawlessly, even. Now it won't do what it's intended to do! & I recently formatted my SSD, & reinstalled EVERYTHING, so, very doubtful of any corruption. & I have a very good Internet Security suite installed & config'd properly too. So, WTF is the problem?