Extension won't install
From Joomla! Documentation
Some extensions won't install on Joomla 3.4.0 giving an error of "No file selected. Unable to find install package"
Errors reported[edit]
No file selected. Unable to find install package
(Note that this error is very generic and can apply to many other issues. This is however the only UI error shown as a result of this issue that affects Joomla 3.4.0 ONLY)
Versions affected[edit]
This pertains only to Joomla! version(s):- 3.4.0
What is the cause[edit]
Extra security checks for PHP files were added for file uploads in JFile::upload. Unfortunately these were not disabled for the extension installer meaning any uncompressed zip files were interpreted as insecure and therefore not installed.
How to fix[edit]
Ensure that your zip files are properly compressed before installing
Apply the following patch https://github.com/joomla/joomla-cms/pull/6180 (this will be shipped in Joomla 3.4.1)