Apple has required App-Specific passwords for quite some time now. App-Specific passwords are used for third party Apps that access Apple’s online services like iCloud. You are only allowed 25 App-Specific passwords. I think what can happen over time is you create an App-Specific password for an App, but then stop using that App down the road sometime. Even though you have stopped using the App, you have still used up one of your 25 App-Specific passwords. At some point you may need to Delete some of the App-Specific passwords you no longer use. Here is how to do that.
App-Specific Password Deletion
To Delete and App-Specific password first login to your AppleID account. Then scroll down to the “Security” section. Once inside the Security section click on the “Edit” button:
You will be taken to this window:
Click on “View History” adjacent to App-Specific passwords:
You will see a list of all the App-Specific passwords associated with this Apple ID:
To remove an App-Specific password just click on the Delete “X” to the right of the item. You will received a warning message like this:
Click on “Revoke” and the App-Specific password is removed freeing up space for a new App-Specific password in the future.
Just an aside, if you look at the bottom of the above window, you will see a button “Revoke All” for removing all of the App-Specific passwords. I am not sure too many people would use this, but perhaps if you were closing out an Apple ID or something.
It is a good idea to clean up your App-Specific passwords from time to time. In that way you will always have enough App-Specific passwords to use for future Apps.