Update Package Install Failed
From Joomla! Documentation
After clicking on updading to Joomla! 3.6.0 via Joomla! Update component, under certain circumstances, Joomla! didn't properly download the file displaying this error message:
ERROR: The archive file is corrupt, truncated or archive parts are missing
This pertains only to Joomla! version(s): 3.6.0
What is the cause
How to fix
Clear manually the files located in your /temp directory (except the index.html file) and clear your cache (site and admin).