ubuntu openOfficePlugin Mendeleydesktop can not install

I have been using Libreoffice from the time since it was first released. I have been upgrading newer version soon after it asked me when it will release.
I am using LibreOffice 6.1 in ubuntu 18.03 and willing to use Mendeley latest version 1.19.2
When I tried to install LibreOfficePlugin through Mendeley tools, I got warning message as like “Couldn’t Install LibreOffice Plugin The LibreOffice unopkg utility gave the following output: /usr/lib64/libreoffice/program/unopkg: 98: exec: /usr/lib64/libreoffice/program/unopkg.bin: not found”
I am bit worried what to do next?
I searched several references but not found solution.
I will be fortunate to get help step by step.
Thanks in advance.
Chitra Baniya