I attempted to update XCode using the App Store app yesterday and was presented with the message “To update this application, sign in to the account you used to purchase it.”. This message however did not point to the real reason why it didn’t work.

What I did was disabling Spotlight Search indexing some time ago, because it affected performance. Turns out, the App Store app uses Spotlight search and in order for XCode to update, it needs to be turned on.

To turn Spotlight Search on, open a terminal and type the following:

sudo mdutil -a -i on

Also make sure you are signed in to your iTunes-Account.