running audacity 2.1.0 on win 7. Extracted mp3 from video with avidemux. Media player plays the file. cannot open it in audacity.
Try opening up the video in Audacity.
You should have the FFMpeg (advanced formats) and probably the Lame (make MP3) software installed.
cannot open either mp4 or mp3 file. Both are marked with red dot with white x. can play the mp3 with VLC media player. Here is a link to the file: https://jayaleavitt.tonidoid.com/urlcedgz0.
That file opens fine here.
What happens when you try to open it?