Source:http://bookingtohosting..com/2015/08/can-not-update-apps-from-app-store-as.html

ISSUE:- WHEN TRYING TO UPDATE ALL APPS FROM MAC APP STORE, IT ASKS PASSWORD FOR AN OLD OR SOMEONE'S APPLE ID WHICH IS GRAYED OUT AND CAN NOT BE CHANGED.


"Apps can not be updated as the App Store asks Password for old or someonelse's Apple ID which is grayed out and can not be changed."

We can get rid of this however you must note that by doing the following you WILL NOT ATTAIN OWNERSHIP of these apps. If you remove the Apple ID and enter your Apple ID then one of two things will happen. Situation A: you do not own that app (it is not listed as a purchase on your Apple account). The App Store yells at you about it that "Update Unavailable with This Apple ID: This update is not available for this Apple ID either because it was bought by a different user or the item was refunded or cancelled.". Situation B: you do own it and the App store allows you to download the latest version in full. Simple as that. You can always download/update apps that are listed under the account you are signed into the App Store with, because, well you know. They’re yours. They are in your account.

Removing the grayed out Apple ID email is as simple as following these quick few steps. Please note that it is impossible to test this with every app in the App Store but I haven’t seen anything to say that this isn’t the way it works for all apps.


Go to the app listed in the App Store as needing an update (usually in the /Applications folder).

Right click the app then click “Show Package Contents”.

Go into the “Contents” folder, then into the “_MASReceipt” folder.

Delete the “receipt” file (you may need to enter a local administrator username and password).

Please note that the app will still work as intended.
That’s it. This is really only useful in if the app you need updated is already in your Apple ID account. But even then deleting the app, logging into your Apple account, finding it in the App Store, and downloading it accomplishes the same thing.
Now, close the Mac App Store and then launch it again. Hopefully, at this point, when you try to update the app, its Apple ID field will be empty.If this doesn't work, you will probably want to put the _MASReceipt folder back, by opening the Trash.

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