Amazon Advertising recently migrated all Seller Central accounts to the Amazon Advertising Console.  This means all vendors, sellers and book sellers (KDP) will now access the same advertising platform. With that, Amazon Advertising has changed up some of their naming conventions and IDs.

Whenever Prestozon refers to an account ID, we are referring to what is now known as the Merchant Token.  Here is where you can find that on the Amazon Advertising Console (note that you may need to be an administrator to access some of these windows):

Go to Settings in the top right corner of the Ad Console and click Account Info:

From there, select the Merchant Token link:

This is your Merchant Token:

Amazon may continue to change these IDs and structures as they finalize the Advertising Console migration, currently this is the best place to find what Amazon refers to as the Account ID (which is the Amazon Account ID you see associated with your account when you're logged into Prestozon).