Failed to fetch basic information about resellers, clients and domains data from source servers
Cause: Command execution failed on the local server with non-zero exit code.
command: rsync -r --chmod=Fu=r,Du=rwx,go= --timeout=30 -e 'ssh -i /usr/local/psa/var/modules/panel-migrator/sessions/20180521080203/ssh-keys/id_rsa.xxxxmyipxxxxx-p 27653 -o PasswordAuthentication=no -o StrictHostKeyChecking=no -o GSSAPIAuthentication=no' /usr/local/psa/admin/plib/modules/panel-migrator/backend/lib/python/parallels/plesk/source/legacy/extras/plesk_17_0_pmm_shared/ root@xxxxmyipxxxxx:/tmp/plesk_migrator-ex8zpzy78niseaodloax8zbi4p08vym3/pmm_agent
exit code: 255
stdout:
stderr: Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: unexplained error (code 255) at io.c(226) [sender=3.1.1]

That is a critical error, migration was stopped.

Failed to connect to the source server 'source' (xxxxmyipxxxxx) by SSH: not a valid EC private key file