The app was purchased through VPP and synced to intune successfully and assigned this app to a security group (user-based) as required.
The devices that were used by users are corporate-owned and supervised with some lockdown features.
When the app was deployed to a user-based security group, users were prompted to key in the credentials.
Since the Apple store is restricted by the DEP profile, users cannot sign into the store.
Following is the error message on the device:
Sign in to the associate account. Please sign in to use your iTunes account for licenses assigned to you by your administrator.
From the intune portal, app installation status for the user, it has the following error message.
VPP App licensing pending user consent ensure the user has accepted the VPP management invite (0x87D13B92)
Based on the above screenshots, i have looked at the volume purchased app assignment in the intune portal.
Following is the assignment settings for the app.
And looking at the VPP application, the app was purchased with a device license.
When you purchase an app with a device license and during the assignment, the license type chooses as 'User'.
When you add the group to the VPP app, the default license type is user and if you don't notice this and simply save the settings, end-users will receive a notification to sign in to the associate account.
Following is the Microsoft article on the same https://docs.microsoft.com/en-us/mem/intune/apps/vpp-apps-ios#how-are-purchased-apps-licensed
To fix this issue, go back to the app assignment, click on the license type and change the setting to device license and save the changes.
This is one time action and you are not allowed to change the license type from device to user.
After sometime, iOS device will receive the updated settings and allow them to use the application.