backup restore doesn't work

[mist_firefly]

one of our clients did a backup in their personal ftp repository of their website.
He now wants to restore the domain to that state but when trying to restore get's an error on plesk control panel:

pmm-ras error (Error code = -6):
==STDOUT======================
================================
==STDERR ======================
terminate called after throwing and instance of 'plesk ::CurlException

so it didn't work .. how can I do the restore?
I have the tar file is there any other way to try it?

I wanted to use the following command in the command line
/usr/local/psa/bin/pleskrestore --restore /var/lib/psa/dumps/clients/<client>/domains/<domain>/<prefix|domain>_info_<timestamp>.xml –level domains


but I have a tar file so I unziped it and it has a few folders and files in ..one of them is an xml..would that be ok to use?
is there a different way to do it?

Pls help

[mist_firefly]

Ok what we now did:

unzipped the tar file and run the command
/usr/local/psa/bin/pleskrestore --restore ...
This restored the domain back ..or so we think but we got an error

close failed: [Errno 32] Broken pipe

What could this mean?

Also I had this xml backup on a different domain(domain2) because I wanted to test it first..but it still restored the domain tat was in the backup(domain1) . which i guess it makes sense but is there an option of taking a backup from domain1 and uploading/restoring it on domain2 to actually test the outcomes of this before restoring to domain1?(if that makes sense)