Intune App Protection Policies (APP, also known as MAM) introduced a product enhancement to request the user PIN when biometric information changes on iOS (TouchID/FaceID) to further protect organizational data. The change introduced a bug that causes Intune APP to incorrectly detect a biometric change and prompt the user with a PIN challenge. This PIN challenge will only occur when switching between two APP managed apps and if the apps have adopted the SDK with this bug.
The bug was introduced in the Intune APP SDK for iOS v. 8.1.0. The bug has been fixed in the Intune APP SDK for iOS v 9.0.1. App teams adopt the new SDK and then run the apps through their testing and release processes. We will update this post when we hear all the new app teams have adopted the new SDK.