I'm trying to get the "App and Book Information" of the custom app, but the result is empty.

I'm looking at the Apple official document below and getting the app's information. https://developer.apple.com/documentation/devicemanagement/getting-app-and-book-information-legacy

However, I couldn't get the custom app's information for a few days ago. The result item is empty.

This is a URL that is normally viewed. https://uclient-api.itunes.apple.com/WebObjects/MZStorePlatform.woa/wa/lookup?version=2&p=mdm-lockup&caller=MDM&platform=volumestore&cc=jp&id=1202716089

This is the URL that gives an empty response to the result. https://uclient-api.itunes.apple.com/WebObjects/MZStorePlatform.woa/wa/lookup?version=2&p=mdm-lockup&caller=MDM&platform=volumestore&cc=jp&id=1556411142

In ABM/ASM, the number of applications used and the number of available applications are all viewed normally.

Is there anything else I can check? Please reply. Thank you.

https://developer.apple.com/documentation/devicemanagement/getting-app-and-book-information-legacy#Authenticate-for-Custom-Apps documents some additional authentication you must do for custom apps. Custom apps are only available to specific organizations that the developer has allowed, so you need this extra authentication material to identify your organization.

I'm trying to get the "App and Book Information" of the custom app, but the result is empty.
 
 
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