Emacs can't find package to install

Question

I got this error when trying install Emacs package automatically.

Warning (initialization): An error occurred while loading `/Users/username/.emacs.d/init.el':

File error: http://melpa.org/packages/projectile-20150619.800.el, Not found

To ensure normal operation, you should investigate and remove the
cause of the error in your initialization file.  Start Emacs with
the `--debug-init' option to view a complete error backtrace.

Answer 1

You need to first refresh ELPA package archives by M-x package-refresh-contents, because yours are out-of-date so the package manager can't download package for you.

You can also install packages from Package Menu (entering via M-x list-packages), refreshing will be done automatically.