If you are getting the below error while updating the Plesk versions or installing the microupdates , have a try with the mentioned solution :
ERROR: Unable to download the MD5 sum for the new Parallels Installer binary.
Not all packages were installed.
Please, contact product technical support.
Remove cache from /var/cache/parallels_installer/ and start auto-installer again.
If you require help, contact SupportPRO Server Admin