When importing a backup from another Plesk server, one of the following error messages appears in Plesk:
PLESK_ERROR: Error: Unable to upload the backup file (backup_info_<number>.xml.tar). The file was modified, corrupted, created on another server or in an older Plesk version that does not support signing of backups. If you trust this backup, then select the “Upload backup files without valid signatures” option and repeat uploading.
When importing a backup via a command-line interface, the following error message is shown:
# plesk sbin pmm-ras –import-file-as-dump –dump-file-specification </path/to/backup_info_<number>.xml.tar>
exit status 116
Plesk backups are encrypted with the Plesk encryption key, which is unique for each Plesk installation. Plesk backups cannot be restored on another Plesk server without the option Upload backup files without a valid signature.
Follow the instructions from this KB article.