In the long and storied history of Apple’s operating systems, few releases have been as pivotal as . Released in July 2011, Lion was not just another annual update; it was a paradigm shift. It marked the moment Apple fully committed to blurring the lines between its mobile iOS devices and its traditional desktop computers.

Before Lion, updating your Mac involved a trip to the Apple Store (physical) or waiting for a CD/DVD in the mail. You would insert the disc, restart, and run the installer. With Lion, Apple took a gamble on internet infrastructure.

Even when you find the Lion installer in the App Store, you will likely encounter errors. Below are the most frequent problems and their solutions.