"One or more Client IDs entered was invalid"

Problem Overview

When you try to allowlist an API key in the admin console under Enterprise Settings or Business Settings > Apps > Custom Apps > Settings > Disable unpublished apps by default, you receive this error:

Root Cause

• The API key you entered is associated with a published application. You do not need to allowlist published applications. Instead of allowlisting a published application, you can add the application. To add a published application, search for the application's name in the Box App Gallery, then click the title of the of the app you want to add, and then follow the instructions.
• The API key was previously added to the "except for" list.