Parallels Plesk Automation upgrade failed, following error can be found in the log
2013-12-24 14:12:27,194 [ERROR]: The server doesn't meet system requirements. At least 4096 MB of memory are required for Parallels Plesk Automation, but only 3948 MB is available on the node.
RAM does not meet PPA requirements.
According to PPA 11.1 release notes Management Node should have minimum 4GB of RAM.
To fix the issue increase amount of RAM at least to 4096 MB.