Hi @Daniel McDonnell Thanks for posting in our Q&A.
Make sure the VPP app assignment as "Required". The Available deployment intent is not supported for device groups, only user groups are supported.
When updating a VPP app, it can take up to 24 hours for the device to receive the updated VPP app. The device must be unlocked and available to install the update successfully. More details about manage VPP apps, please refer to: https://learn.microsoft.com/en-us/mem/intune/apps/vpp-apps-ios#assign-a-volume-purchased-app
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