Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
I previously had FFmpeg 4.2 installed on my Windows computer. I installed ImageMagick 7.0.8-62 Q16 and it includes FFmpeg 3.4, which is older and doesn't support palettegen correctly. Unfortunately ImageMagick got ahead of FFmpeg on the path and I spent way too much time trying to figure out why palettegen stopped working.
Check to see if FFmpeg is installed before installing an older version
Update the installer to include the latest version of FFmpeg
If ImageMagick needs the older version of FFmpeg then put it in a sub-directory that isn't on the path