Issue: Any attempt to unpack/unzip a Plesk backup using 7zip or WinRAR results in a compression method not supported message and the Plesk backup files and database show 0 KB.
Cause: As a new feature, Plesk picked up the Zstandard (zstd) compression method for backups. Current archive programs like 7zip and WinRAR don't support this compression method.
Resolution: There are two resolutions. One is to modify the Plesk panel.ini file to use the old/classic compression method. The second is to download and install the 7-Zip-zstd application
Resolution 1: Open the panel.ini file in a file editor. The file can be located at admin/conf/panel.ini. Add these lines to the appropriate place. The [pmm] section may already exist. If so just add compressionMethod = deflate below it.
compressionMethod = deflate