Hello. I’ve been using Audacity 2.4.2 for a few days, and been faced with this issue now. When I tried to import a slightly bigger file than the ones I’ve been importing (13-14MB), the warning from the title appears and it seems I’m unable to import anything above 10MB.
What does this error mean exactly? How can I solve this?
It means that there’s a problem with that MP3 file.
You could try converting the MP3 to WAV with another program (such as foobar2000), then if that works you will be able to import the WAV file into Audacity.
I just encountered this issue, and the MP3 file was not corrupted. It opened just fine in iTunes, where I converted it to an ACC file,which I was able to open in Audacity. The file is a practice track for a quartet I sing in, and I had just previously been playing it out of Dropbox on an iPhone, so I wonder if that had something to do with the error. In any case, my solution of using iTunes as an intermediary solved my issue satisfactorily.
Audacity 2.4.2 is very fussy about MP3s. They have to strictly conform to the MP3 standard, otherwise Audacity will refuse to import them. This increased strictness was to fix a problem with non-standard files being misidentified. The next version of Audacity will be less strict / more forgiving about MP3s, so we should see a lot less problems of this sort.
Why not put a warning on potentially problematic files then? It seems absolutely nuts to outright refuse to open a perfectly workable file. I’ve never had any issues before and suddenly I can’t load around 40% of my library into Audacity.
Why not put a warning on potentially problematic files then?
As your quote says, the developers are working on change for the next version.
Previously, Audacity would open files that were misnamed as MP3 but were actually a different format and you’d get a garbage file full of useless noise. So, the change was intentional but we are finding-out that lots of people have corrupt or non-compliant MP3s.
It seems absolutely nuts to outright refuse to open a perfectly workable file. I’ve never had any issues before and suddenly I can’t load around 40% of my library into Audacity.
At least now you know you’re perfectly “workable” MP3s aren’t technically perfect. 
Yet I can load 100% of mine. I guess it depends on where you get your MP3s.
Personally I’m very surprised that we are seeing so many MP3s with header problems - I doubt that many people would have predicted that.
This has already been done in the development code.
I’m not gonna pretend like I could have foreseen the scope of the problems but no matter what you expected, it is a weird way to handle the issue. Full stops like this one should only be used as an absolute last resort, not as a go-to solution.
Well, I loaded the mp3 file in 2.3.2 a half hour ago but in 2.4.2 now I get the error message. I know it’s a valid mp3, too. This is crazy.
BTW, when did the edit shortcuts (command-A, command-C, command-V, etc.) stop working in the Export windows? They are greyed out and I now have to type every field by hand, even when the text is the same (such as song and album titles being the same).
Looks like I’m going to be reinstalling an earlier rev. 
Try this:
If you don’t already have “FFmpeg for Audacity” installed, follow the instructions here to install it: Installing FFmpeg for Windows - Audacity Manual
Then in
“Edit menu > Preferences > Import / Export > Extended Import Preferences”
Click the “Add new rule” button, and name the new rule: *.mp3
Then in the right hand column, move “FFmpeg-compatible files” to the top, like this (below), and then click the “OK” button.
The drawback of this method is that MP3s will be imported as 16-bit tracks. It is highly recommended to convert the track to “32-bit float” format immediately after import (see “Format” in the track dropdown menu: Audio Track Dropdown Menu - Audacity Manual)
