Can't open m4a file

To me it looks like the file is just a wrapper with no data.

Try playing it in VLC which will play just about anything (and is free). If VLC chokes on it then the file is corrupt.

Get info on the file. To me it sounds like something did not go correctly in saving it from Mail to your computer.

FWIW I often zip files I don't want the mail app to modify or potentially corrupt in any way while in transit.

Try uploading the file in Google Drive and try playing it inside

If this is an Apple Music file it isn't designed to be redistributed and it has DRM protection.

I suspect that even though it is Android "m4a" it is not Apple m4a. It may have some strange flavor mp4-audio codec that Apple's list doesn't contain but VLC is built for pretty much everything. I have seen this in some mp3s in the past too.

I probably can't help you then. I am running a much older OS version and maybe this is a Big Sur issue. Plus I have never opened a sound file in Mail. All I know is that occasionally I encounter audio files that don't behave as expected and I need to re-process them such as using VLC with passthrough to get the file to work. I have never used Android. Maybe the m4a it produced wasn't really mp4 compliant? What codecs were used? There's lots of ways to approach this.

You don't have an iTunes app in Big Sur.

Yep.

So old I forgot about it.

nq wrote:

I'm still confused as to why this file won't play in an Apple app.

You and me both. If it plays in Apple Mail, it should play in QuickTime Player, Quick Look, Safari, etc.