Why do I receive APP_KEY_CREATION_FAILED when making a createDeveloperAppKeys request?

You are attempting to create an Application Key for an account that has already had them assigned. Each account is assigned a unique set of Application Keys; once you have successfully created your set of Application Keys you cannot create additional keys. 

Use the “getDeveloperAppKeys” operation as instructed below to retrieve the Application Keys you created previously.

How to Retrieve Existing Application Keys

To retrieve your existing Application Keys:

1. Click on the Accounts API Demo Tool link 
2. Select thegetDeveloperAppKeys operation from the list of Operations on the top left-hand side of the demo tool.
3. Enter a sessionTokenin the 'Session Token (ssoid)' text box.  You can find instructions on how to find your sessionToken via your browser here.
4. Press Execute at the bottom of the 'Request' column.
5. Details of your existing Application Keys will then appear on the right-hand side under the Developer Apps column.
6. The Application Key value is shown under the Application Key column. Please note: You need to expand the Application Key column to see the full Application Key value which is 16 characters in total.