My app refuses to work unless I have a vpn enabled
Android Nougat adds a feature whereby Android for Work apps can declare in their security configuration that the app can only work when connected to a VPN, for security reasons. There's a quick description of the feature (amongst other Nougat features) in this Ars Technica article. This page on the Android Developers website describes how the app developer can control the feature, but the description is very technical and a bit impenetrable.

The restrictions added inside the app interact with the Device Administrator app (such as AirWatch), so that your IT department can set a security policy that enables or disables the restrictions (just like any restrictions on password length).