Musescore 4 - Corrupted file. Can't decompress .mscz file

Files which cannot be opened by 7zip or similar are damaged beyond repair. Sometimes they contain only zeros, their file length is zero or the zip structure is too damaged. Open the file with a simple text editor to check this.

Try to find a backup copy in one of the following folders (Windows):

• C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4
• C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4\cloud_scores
• C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4\cloud_scores.mscbackup
• C:\Users\{YourUserAccount}\Documents\MuseScore4\Scores
• C:\Users\{YourUserAccount}\Documents\MuseScore4\Scores.mscbackup
• C:\Users\{YourUserAccount}\Documents\MuseScore4\Cloud Scores

In "AppData" (hidden folder) the files have cryptic names so orientate yourself by the date of saving.
For the backup files you have to rename the extension: Delete the tilde or comma at the end.

An upload of MuseScore files should work, what is the problem? The forum accepts only some file types but mscz, mscx, zip, png and some others should not be a problem.