Q: Problems downloading with App Store

Back up all data.

Quit the App Store if it's running. Force quit if necessary.

Please triple-click anywhere in the line below on this page to select it:

defaults write -app "App Store" ShowDebugMenu YES

Copy the selected text to the Clipboard by pressing the key combination command-C.

Launch the built-in Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.

Paste into the Terminal window by pressing the key combination command-V. I've tested these instructions only with the Safari web browser. If you use another browser, you may have to press the return key after pasting.

Wait for a new line ending in a dollar sign ($) to appear below what you entered. You can then quit Terminal.

Launch the App Store. There should now be a menu labeled Debug in the menu bar at the top of the screen. From that menu, select

Reset Application

defaults delete -app "App Store" ShowDebugMenu