Sorry if this is a duplicate, but it'd be awesome if Casper had a notification system to tell us if apps have been removed from the apple store and therefore are no longer deployable.
As of Jamf Pro 10.1.0, Apps removed from the App Store that are using VPP licenses will automatically be disabled. When viewing the App catalog record in Jamf Pro, a message bar will appear on top of the screen indicating the App was removed from the App Store. When viewing the list of Apps in Jamf Pro, those disabled due to being removed from the App Store will appear with a warning icon as well as greyed out text. Apps in a disabled state will no longer issue installation commands and will no longer assign VPP licenses. These Apps will also no longer appear available for installation via Self Service.
As of Jamf Pro 10.2.0, VPP Account Notifications can be configured to send an email digest with a Trigger of "Item removed from the App Store.” The Notification can be configured for a single or multiple VPP Accounts and can be sent to any desired email account. The digest of content falling into this state will be emailed once a day. This feature is available by navigating to Settings, Global Management, VPP Accounts and selecting the Notifications tab.