How to Fix OS X Mountain Lion Error 100 Download Errors

OS X Mountian Lion is live in the Mac App Store for $20, but some users are having trouble downloading the OS X Mountain Lion installer to their Mac after purchase.

The errors range from, “This item is temporarily unavailable. Please try again.”, to the annoying error 100 message which delivers a less than helpful, “We could not complete your App Store request. An unknown error occurred (100).”

Fixing the Mac App Store error 100 issue will take a few minutes, and then you’ll be on your way to downloading the latest version of OS X.

How to Fix Mac App Store Error 100 (Easy)

Mac app Store Error 100

Quit the App Store.

The first step to try is an easy one, but it doesn’t always fix the problem, so if this doesn’t work be prepared to go on to the more advanced error 100 fix.

Sign out of the App Store – Click on Store in the Menu Bar – choose Sign out.

Click on the App Store menu in the menu bar and choose Quit App Store.

Restart your Mac and log in to the App Store to try and download OS X Mountain Lion again.

This will fix the issue for many users, but if the problem persists, follow these detailed instructions.

How to Fix the Mac App Store Error 100 (Advanced)

If the previous fix doesn’t clear the error 100 issue with the Mac App Store, Matt Gemmell offers a possible solution.

Quit the Mac App Store – Click on App Store and choose Quit App Store.

Delete old “Install OS X Mountain Lion” installers. This step is aimed at developers, or users who otherwise tested OS X Mountain Lion ahead of the release.

Delete the “~/Library/Caches/” folder.

  • To get there, click on Finder and click on Go in the Menu Bar.
  • Choose Go to Folder.
  • Paste the address in the box that appears.
Fix Mac App Store Error 100 Step 2

Delete this folder to fix the Mac App Store Error 100 message.

Select the folder and Move to trash.

Launch the Mac App Store and attempt to download OS X Mountain Lion again.